The present invention relates to a storage battery system comprising a storage battery and a power conversion device that performs electric conversion between a storage battery and an AC system, and is particularly suitable as a storage battery system for smoothing output changes of renewable energy. [Background Art]
With the conclusion of COP21, the introduction of renewable energy such as solar power generation and wind power generation is accelerating to reduce CO2 emissions worldwide.
However, renewable energy has a drawback in that its output varies depending on climatic conditions. When the input amount of renewable energy becomes larger than the capacity of the grid, it is difficult to adjust the output of existing thermal power plants in order to balance the supply and demand of electric power.
Accordingly, in recent years, in order to make it possible to adjust the output of thermal power plants, when inputting renewable energy, examples of cases are appearing in which electric power system operators are required to limit the power change rate of power generation plants to less than or equal to a predetermined value. As one effective means for complying with this change rate, there is a method of introducing a storage battery system into a power generation plant and suppressing the power change rate of the plant.
Also, as one method of reducing the cost of the storage battery system, Japanese Unexamined Patent Application Publication No.2007-135355 A discloses a method of providing a storage element with a low kWh unit price (capacity unit price) and a storage element with a low kW unit price (output unit price) in a storage battery system, smoothing the low frequency components of the output fluctuation of renewable energy with the charging and discharging of the storage element with the low kWh unit price, and smoothing the high frequency components of the output fluctuation of renewable energy with the charging and discharging of the storage elements of the storage element with the low kW unit price.

[Summary of Invention] [Technical Problem]
As examples of renewable energies to which output smoothing can be applied, in the case of photovoltaic power generation systems when the solar radiation suddenly decreases due to cloud movements or the like, and in the case of wind power generation when the wind speed suddenly drops, it is necessary to supply a large output [kW].
However, when the charging rate of the storage battery or the capacitor is low, the dischargeable electric power becomes less than the dischargeable electric power in the state of a high charging rate. For this reason, even when equipped with a storage battery having a low kW price for mitigating the steep output changes of renewable energy, it is impossible to discharge sufficiently due to the reduction of the remaining Wh amount or the dischargable electric power, and there is a possibility that power plants may be unable to comply with the fluctuation mitigation request. [Solution to Problem]
In a storage battery system configured to connect to a connection point between a power generation source based on renewable energy and an electric power system, in order to solve the above problems, the storage battery system of the present invention includes a plurality of storage battery units! and a storage battery system control device configured to calculate output power command values of the plurality of storage battery units and control the plurality of storage battery units, wherein the storage battery system control device is configured to suppress an output change rate of the power generation source by: setting, in a case that an output fluctuation of active power output by the power generation source toward the electric power system is within a predetermined range, an output power command value for a first storage battery unit from among the plurality of storage battery units to a value with an absolute value that is smaller than an output power command value for another storage battery unit among the plurality of storage battery units, and setting, in a case that the output fluctuation of active power exceeds the predetermined range, an output power command value for the first storage battery unit to a value that increases charging and discharging from the first storage battery unit, and operating in a first

control mode configured to compensate for an insufficient power amount due to charging and discharging from the another storage battery unit.
[Advantageous Effects of Invention]
According to the present invention, even when the output of power supplies based on renewable energies rapidly decrease, it is possible to ensure discharge capacities such that storage battery systems can suppress the power change rates of power plants, and it is possible to improve the compliance rate of power plants with respect to output fluctuation mitigation requests. [Brief Description of Drawings]
FIG. 1 is a diagram illustrating a configuration in which a solar power plant having a storage battery system according to Embodiment 1 is connected to a power system.
FIG. 2 is a diagram illustrating calculation blocks of a storage battery system control device.
FIG. 3 is a diagram illustrating calculation blocks in an individual control device 2000 of the power converter 203.
FIG. 4 is a diagram illustrating calculation blocks in an individual control device 3000 of the power converter 303.
FIG. 5 is a diagram illustrating characteristics at an operation time of Embodiment 1 in chronological order.
FIG. 6 is a diagram illustrating a calculation block of a storage battery system control device having another form of a fluctuation suppression storage battery system power calculation unit.
FIG. 7 is a diagram illustrating another form of calculation blocks in the individual control device 2000 of the power converter 203.
FIG. 8 is a diagram illustrating a configuration of the form of another system to which Embodiment 1 is applied.
FIG. 9 is a diagram illustrating calculation blocks of the storage battery system control device according to Embodiment 2.
FIG. 10 is a diagram for explaining a change in the output of solar power generation. [Description of Embodiment(s)]

Hereinafter, Embodiments 1 and 2 will be described below with reference to the Figures as embodiments of a power storage system according to the present invention. [Embodiment l]
FIG. 1 is a diagram illustrating a configuration in which a solar power plant 600 having a storage battery system 1 according to Embodiment 1 of the present invention is connected to a power system 5.
The storage battery system 1 is provided in conjunction with a solar power generation system 40, which serves as one type of renewable energy, and has a function of suppressing an output change rate of the solar power generation plant 600.
The solar power generation plant 600 is connected to the electric power system 5, and the solar power generation system 40 and the storage battery system 1 are electrically connected to this connection point.
The main circuit of the solar power generation system 40 is constituted by a solar panel 404, a power converter 403, and a transformer 402. The power converter 403 converts DC power generated by the solar panel 404 into AC power having the same frequency as that of the power system 5, and outputs the AC power to the power system 5 via the transformer 402.
The storage battery system 1 is primarily constituted by two storage battery units 20, 30, active power measurement units 10, 11, and a storage battery system control device 100. The active power measurement unit 10 measures the active power (P_PLANT) output by the photovoltaic power generation plant 600 to the power system 5, and the active power measurement unit 11 measures the active power (P_PV) output by the solar power generation system 40 to the power system 5. Each of the respectively measured and detected active powers (P_PLANT and P_PV) are output to the storage battery system control device 100 via a communication network (not illustrated in the Figures).
The main circuits of the storage battery units 20, 30 are respectively constituted by storage batteries 204, 304, power converters 203, 303 and transformers 202, 302. The power converters 203 and 303 input and output power to and from the power system 5 via the transformers 202 and 302, whereby the storage batteries 204 and 304 are charged and discharged.
The voltage and current of the storage batteries 204, 304 are detected by the

voltage sensors 205, 305 and the current sensors 207, 307, and the respectively detected values are output to the battery controllers 206, 306. The battery controllers 206 and 306 respectively calculate the charging rates SOCl and SOC2, the dischargeable powers P_Maxl and P_Max2, and the chargeable powers P_Minl and P_Min2 of the storage batteries 204 and 304. The outputs of the battery controllers 206 and 306 are output to the storage battery system control device 100 via the communication network (not illustrated in the Figures), and the charging rates SOCl and SOC2 are also output to the individual control devices 2000 and 3000 provided in the power converters 203 and 303.
The individual control devices 2000 and 3000 of the power converters 203 and
303 respectively input the storage battery charging rates SOCl, SOC2 calculated by the battery controllers 206, 306 and the output power command values P_Refl, P_Ref2 for suppressing the output change rate of the solar power generation plant 600 received from the storage battery system control device 100 via the communication network (not illustrated in the Figures). In addition, charging rate control power command values (P_SOCl, P_SOC2) for reducing the deviation between the charging rate command values and the charging rates SOCl, SOC2 of the storage batteries 204,
304 are calculated, output to the system control device 100 via the communication network (not illustrated in the Figures).
In contrast, the electric power converters 203 and 303 set the sum of the charging rate control power command values (P_SOCl, P_SOC2) and the output power command values (P_Refl, P_Ref2) for suppressing the output change rate of the solar power generation plant 600 as an active power command value to output to the power system 5, and controls the active power to be outputted to the power system 5 so as to comply with the active power command value.
The active power that is output from the electric power converters 203 and 303 to the power system 5 via the transformers 202 and 302, that is, the active power (P_BESS1, P_BESS2) output from the storage battery units 20 and 30, is measured by the active power measurement units 201 and 301, and the output thereof is output to the storage battery control system 100 via the communication network (not illustrated in the Figures).
The storage battery system control device 100 respectively inputs, via the communication network (not illustrated in the Figures), the outputs (P_PLANT, P_PV,

P_BESS1, P_BESS2) of each active power measurement unit (10, 11, 201, 301), the charge rate control power command values P_SOCl, P_SOC2, the storage battery charge rates SOCl and SOC2, the dischargeable power P_Maxl and the chargeable power P_Minl of the storage battery 204, and the dischargeable power P_Max2 and the chargeable power P_Min2 of the storage battery 304, and displays this received data on the display 110.
In addition, the storage battery system control device 100 calculates the output power command values (P_Refl, P_Ref2) for suppressing the output change rate of the solar power generation plant 600, outputs them to the storage battery units 20 and 30 via the communication network (not illustrated in the Figures), and suppresses the output change rate of the solar power generation plant 600.
In Embodiment 1, according to the above configuration, the storage battery system 1 can perform charging and discharging to suppress the output change of the solar power generation system 40.
FIG. 2 is a diagram illustrating calculation blocks of a storage battery system control device 100. One novel aspect of the present invention is that the storage battery units 20, 30 that constitute the storage battery system 1 are divided between a storage battery unit configured to perform charging and discharging to suppress the output fluctuation of the solar power generation system 40 during normal operation time, and a storage battery unit configured to perform discharging to suppress fluctuation in the output of the power plant only when the output change of the above-described solar power generation system 40 is drastic.
The calculation block of the storage battery system control device 100 is generally constituted by a fluctuation suppression storage battery system power calculation unit 1100 and a power distribution unit 1200 configured to distribute, to the storage battery units 20 and 30, the output power command values for suppressing the output change rate of the solar power generation plant 600. In the present Embodiment 1, a configuration is illustrated in which an output change width per unit time of the solar power generation plant 600 is suppressed to a predetermined value.
First, the fluctuation suppression storage battery system power calculation unit 1100 will be described. Here, the calculation cycle of the storage battery system control device 100 is denoted as AT, and the output fluctuation limit value per unit time of the solar power generation plant 600 is denoted as the conversion fluctuation

upper limit value AP converted in the above-described calculation cycle.
The detected value P_PLANT of the active power output by the solar power generation plant 600 to the power system 5 is input to the first calculation cycle delay block 1001. The output of the first calculation cycle delay block 1001 is the active power output value of the solar power plant 600 at the time of a previous calculation, and is input to the adder 1002 and the subtracter 1003.
By adding the conversion fluctuation upper limit value AP to the output of the first calculation cycle delay block 1001, the adder 1002 calculates the output upper limit value of the active power of the solar power generation plant 600 that is allowed in the present control cycle.
By subtracting the conversion fluctuation upper limit value AP from the output of the first calculation cycle delay block 1001, the subtracter 1003 calculates the output lower limit value of the active power of the solar power generation plant 600 that is allowed in the present control cycle.
In contrast, the active power detection value P_PV output from the solar power generation system 40 and the charging rate control power command value P_SOCl for the storage battery unit 20 to control the charge rate of the storage battery 204 are added by the adder 1004, and this added output and the charging rate control power command value P_SOC2 for the storage battery unit 30 to control the charge rate of the storage battery 304 are added by the adder 1005.
The subtracter 1006 calculates the difference between the output of the adder 1005 and the output of the adder 1002, which corresponds to the active power output upper limit value of the solar power plant 600, and outputs the difference to a limiter 1008 which only allows positive values to pass. The output of the limiter 1008 corresponds to an excess amount of the active power output upper limit value of the solar power generation plant 600 with respect to the sum of the solar power generation system 40 and the electric power for controlling the charging rate of the storage battery.
The subtracter 1007 calculates the difference between the output of the adder 1005 and the output of the subtracter 1003, which corresponds to the active power output lower limit value of the solar power plant 600, and outputs the difference to a limiter 1009 which only allows negative values to pass. The output of the limiter 1009 corresponds to an insufficient amount of the active power output lower limit value of

the solar power generation plant 600 with respect to the sum of the solar power generation system 40 and the electric power for controlling the charging rate of the storage battery.
Each of the outputs of the limiter 1008 and the limiter 1009 are added by an adder 1010, and the sign of the output is inverted by the multiplier 1011. The output of the multiplier 1011 is the output power command value of the storage battery system 1 for suppressing the change rate of the active power output from the solar power generation plant 600, and serves as the input to the power distribution unit 1200.
It should be noted that, in the present Embodiment 1, although an example was illustrated in which the calculation performed by the fluctuation suppression storage battery system power calculation unit 1100 depicted in FIG. 2 was used in order to suppress the output change rate of the solar power generation plant 600, alternatively, as illustrated as another form of the fluctuation suppression storage battery system power calculation unit 1100 in FIG. 6, a high pass filter operation on the sum of the output P_PV of the solar power generation system 40 and the charging rate control power command values P_SOCl and P_SOC2 may also be used. That is, the high-pass filter 1020 performs an arithmetic operation on the output (P_PV + P_SOCl + P_SOC2) that passed through the adders 1004 and 1005, the sign is inverted by the multiplier 1011, and the output is input to the power distribution unit 1200. By means of the high-pass filter operation, it is possible to pass the harmonic components of the plant output fluctuation, and to output an output power command value for suppressing (compensating) the harmonic components.
Next, the power distribution unit 1200 of the next stage will be described. In the case that the output fluctuation of the solar power generation system 40 during normal operation is compensated by the storage battery unit 30 and an output fluctuation that cannot be compensated for by the storage battery unit 30 occurs with respect to the active power P_PV output from the solar power generation system 40, the power distribution unit 1200 performs a function of distributing the output power command values in order to output compensation power from the storage battery unit 20.
In particular, the output power command values output from the fluctuation suppression storage battery system power calculation unit 1100 are input to the limiter 1012. The limiter 1012 performs a limiter calculation with the dischargeable

power P_Max2 and the chargeable power P_Min2 of the storage battery 304 as calculated by the battery controller 306 of the storage battery unit 30 as the upper and lower limits, and calculates the output power command value P_Ref2 for suppressing the output change rate of the solar power generation plant 600 for the storage battery unit 30.
In addition, the difference between the output of the fluctuation suppression storage battery system power calculation unit 1100 and the output of the limiter 1012 is calculated by the subtracter 1013, and the output thereof is input to the limiter 1014.
The limiter 1014 performs a limiter calculation with the dischargeable power P_Maxl and the chargeable power P_Minl of the storage battery 204 as calculated by change rate of the solar power generation plant 600 for the storage battery unit 20.
the battery controller 206 of the storage battery unit 20 as the upper and lower limits, and calculates the output power command value P_Refl for suppressing the output
The output power command values P_Refl and P_Ref2 for suppressing the output change rate are output to the storage battery units 20 and 30 via the communication network (not illustrated in the Figures).
As described above, since the storage battery units 20 and 30 control the active power output to the power system 5 in accordance with the output power command values P_Refl and P_Ref2 for suppressing the output change rate of the solar power generation plant 600, it is possible for the storage battery unit 30 to compensate for the output fluctuation of the solar power generation system 40 during normal operation, and for the storage battery unit 20 to assist in power compensation when the output fluctuation of the solar power generation system 40 is large.
Next, calculation of active power command values in the individual control devices 2000, 3000 provided in the power converters 203, 303 of the storage battery units 20, 30 will be described.
FIG. 3 is a diagram illustrating calculation blocks in the individual control device 2000 of the power converter 203.
The charging rate SOCl of the storage battery 204 calculated by the battery controller 206 and the output power command value P_Refl for suppressing the output change rate of the solar power plant 600 calculated by the storage battery system

control device 100 are used as inputs, and the charging rate control power command value P_SOCl and the output power command value P_Refl _New that the power converter 203 outputs to the power system 5 are calculated.
The charging rate SOC 1 is input to the subtracter 2001, and the subtracter 2001 calculates a difference between an externally designated predetermined charging rate command value SOC_Refl and outputs it to the multiplier 2002. The value gain-corrected by the multiplier 2002 is limited by the limiter 2003 to be limited within the upper and lower limit values P_SOCMax and P_SOCMin of the charging rate control power command value P_SOCl. After the sign of the output of the limiter 2003 is inverted at the multiplier 2004, it is output to the storage battery system control device 100 and the adder 2005 as the charging rate control power command value P_SOCl.
The adder 2005 adds P_Refl and P_SOCl to calculate a new output power command value P_Refl_New for the power converter 203. The power converter 203 performs active power control so that the active power output to the power system 5 matches the new output power command value P_Ref l_New.
FIG. 4 is a diagram illustrating calculation blocks in the individual control device 3000 of the power converter 303.
Here, the charging rate command value SOC_Refl of the storage battery unit 20 is set to a value higher than the charging rate command value SOC_Ref2 of the storage battery unit 30 so that the compensation power at the time of a drastic output decrease of the solar power generation system 40 can be output. In the present Embodiment 1, SOC_Refl is set to 80%, and SOC_Ref2 is set to 50% such that both charging and discharging can be supported. The charge rate command values SOC_Refl and SOC_Ref2 are command values instructed in advance, and may be modified as necessary.
By increasing the charge rate command value SOC_Refl of the storage battery unit 20, since the storage battery unit 20 can sufficiently store the storage energy of the storage battery 204, it is possible to increase the output fluctuation compliance rate of the solar power generation plant 600 even in cases in which the active power output from the solar power generation system 40 suddenly drops. In addition, by increasing the charging rate and allowing time to pass, since the kW discharge capacity can also be secured, it is possible to further increase the compliance

rate of output fluctuation suppression.
In the above description, although the charging rate command value SOC_Refl of the storage battery unit 20 was set to 80%, a configuration in which the charging rate command value SOC_Refl can be switched may also be utilized. In another form of the individual control device 2000 depicted in FIG. 7, a charging rate command value calculator 2100 is provided. Since the deterioration progression of the storage battery becomes faster when the charging rate remains in a high state, in order to prevent deterioration of the storage battery 204, the charging rate command value calculator 2100 may be configured to enable switching of the charging rate command value SOC_Refl, such that the charging rate command value SOC_Refl is suppressed to 50% at night, and adjusted to 80%) during the day, for example. Here, switching is performed according to temporal factors, but the present invention is not limited to this, and may be switched may be performed according to other factors.
FIG. 5 is a diagram illustrating the characteristics at an operation time of Embodiment 1 in chronological order.
In FIG. 5, the sum of the output P_PV of the solar power generation system 40 and the charging rate control power command values P_SOCl and P_SOC2 of the storage battery units 20 and 30 (hereinafter referred to as "sum power Psum"), and a time series characteristic (composite graph) synthesized from the output P_PLANT of the solar power generation plant 600 are illustrated at the top, a time series characteristic of the output P_BESS1 of the storage battery unit 20 is illustrated second, a time series characteristic of the output P_BESS2 of the storage battery unit 30 is illustrated third, a time series characteristic of the charging rate command value SOC_Refl and the charging rate SOCl of the storage battery unit 20 are illustrated fourth, and a time series characteristic of the charging rate command value SOC_Ref2 and the charging rate SOC2 of the storage battery unit 30 are illustrated fifth.
In these time series characteristics, the horizontal axis is time, and the calculations for the storage battery system control devices 2000 and 3000 are performed every time AT. In addition, a value obtained by converting an allowable power fluctuation width during the calculation period AT of the storage battery system control device 100 from the output change width of the solar power generation plant 600 per unit time is denoted as AP.
At time i, the sum power Psum [i] and the solar power plant output P_PLANT

[i] are assumed to be equal. The storage battery system control device 100 controls the storage battery units 20 and 30 such that the plant output P_PLANT [i + l] at the time i + 1 is adjusted within an allowable power fluctuation range between P_PLANT [i] -AP and P_PLANT [i] + AP
The charging rate of the storage battery unit 20 is set to be equal to the charging rate command value SOC_Refl at time i, the charging rate of the storage battery unit 30 is set to be a value smaller than the charging rate command value SOC_Ref2 at time i, and the charging rate control power command value P_SOC2 is calculated such that the difference between the charging rate SOC2 and the charging rate command value SOC_Ref2 becomes smaller.
At time i + 2, since Psum [i + 2] becomes larger than P_PLANT [i + l] + AP, the power command of the storage battery system 1 becomes a charge command. In addition, since the charge command value becomes smaller than the chargeable power of the storage battery unit 30 at this time, a charge command is allocated to the storage battery unit 30 according to the power distribution calculation of the storage battery system control device 100 illustrated in FIG. 2. As a result of the charging of the storage battery unit 30, the output P_PLANT [i + 2] of the solar power generation plant 600 becomes P_PLANT [i + l] + AP, and the change rate constraint can be complied with.
Subsequently, at time i + 7, the output P_PV of the solar power generation system 40 abruptly decreases. Psum [i + 7] becomes much lower than P_PLANT [i + 6] - AP, and the output of the fluctuation suppression storage battery system power calculation unit 1100 becomes a large discharge power command.
At this time, since the above-mentioned discharge power command value exceeds the dischargeable electric power P_Max2 of the storage battery unit 30, the output power command value P_Ref2 for the storage battery unit 30 becomes P_Max2, and the insufficient amount of the discharge electric power instruction becomes the output power command value P_Refl for the storage battery unit 20.
Since the storage battery unit 20 maintains a high charging rate, sufficient discharge is possible, and it is possible to suppress the decrease in P_PLANT [i + 7] to P_PLANT [i + 6] - AP. Until the time i + 9, the storage battery unit 20 continues discharging according to the power distribution calculation of the storage battery system control device 100 illustrated in FIG. 2. In this way, P_PLANT [k] (where k is a

natural number) can transition while complying with fluctuation suppression conditions.
As described above, according to Embodiment 1, even in cases in which the output of the solar power generation system 40 suddenly decreases, the output change rate of the solar power generation plant 600 can be suppressed by discharging from the storage battery unit 20, and it is impossible to improve the compliance rate with respect to the fluctuation suppression request.
In addition, by performing power distribution control that causes the storage battery 204 to perform standby with a high charging rate, even in cases in which the dischargeable power of the storage battery unit 30 that suppresses the output fluctuation of the solar power generation system 40 during normal operation decreases, the likelihood increases that the storage battery unit 20 can perform discharging to limit the output change rate of the solar power generation plant 600 within a predetermined range.
Although the solar power generation system was the target of active power output fluctuation in Embodiment 1, the present invention is not limited to this power generation system. As another power generation system instead of the solar power generation system 40 to which Embodiment 1 may be applied, the wind power generation system 50 illustrated in FIG. 8, for example, can achieve the same effects.
In addition, although the solar power generation system 40 was configured with one power conversion system in Embodiment 1, the solar power generation system 40 may be configured with a plurality of power conversion systems. In that case, by providing an active power measuring unit 11 to detect the total sum of the active power output by the power conversion system, it is possible to achieve the same effect as that of Embodiment 1.
In addition, although the storage battery units 20 and 30 were configured with one storage battery power conversion system in Embodiment 1, the storage battery units 20 and 30 may be constituted by a plurality of storage battery power conversion systems. In that case, with respect to the dischargeable power and the chargeable power, if the dischargeable power and the chargeable power that represent the sum of the plurality of storage battery power conversion systems and the charging rate control power command value are transmitted to the storage battery system control device 100, and the storage battery system control device 100 transmits an

output power command value to each storage battery power converter, the same effects as those of Embodiment 1 can be achieved. [Embodiment 2]
Next, the storage battery system 1 according to Embodiment 2 of the present invention will be described.
FIG. 9 is a diagram illustrating calculation blocks of the storage battery system control device 100_2 according to Embodiment 2. It should be noted that those elements that are similar to those of Embodiment 1 are denoted by the same symbols, and redundant explanation is omitted.
The only difference between the storage battery system of the present Embodiment 2 and the storage battery system of the previous Embodiment 1 is that the storage battery system of the present Embodiment 2 includes a configuration in which the power distribution method of the storage battery system control device 100 is modified according to calendar information. For this reason, the storage battery system control device 100_2 has a configuration in which a power distribution unit 1300 and a calendar function switcher 1400, which will be described later, are added to the storage battery system control device 100 of the previous Embodiment 1. Accordingly, functionally as well, functions (control modes) of the power distribution unit 1300 and the calendar function switcher 1400, which will be described later, are added to the functions (control modes) performed by the storage battery system control device 100 described in Embodiment 1. In addition, in the present Embodiment 2 as well, it is possible to utilize the other forms illustrated in FIG. 6 or FIG. 7 as described in Embodiment 1.
FIG. 10 is a diagram for explaining a change in the output of solar power generation. In the solar power generation system 40, as an example, clouds cover the solar panel 404, and the power generation amount is reduced. With respect to the decrease width in the power generation amount, since the power generation amount cannot become negative, the greater the amount of electric power that can be generated on a day with clear weather becomes, the greater the maximum value of the decrease width becomes. For this reason, as illustrated in FIG. 10, the maximum value of the decrease width increases during the day, which makes compliance difficult for the power change rate of the solar power plant. In contrast, in the early morning or evening, the possible power generation available during clear weather also decreases,

so that the maximum output value required to suppress the output fluctuation decreases.
In time periods during which it is anticipated that the output of the solar power generation system 40 during clear weather will be greater than the first predetermined value, the storage battery system control device 100_2 of the storage battery system 1 according to the present Embodiment 2 causes the storage battery unit 20 to standby with a high charging rate similar to Embodiment 1 in order to guarantee suppression of output fluctuation by the storage battery unit 30 during normal operation. In other time periods, the output power command value for suppressing the output change rate of the solar power generation plant 600 is allocated according to the ratio between the rated capacity P20 of the storage battery unit 20 and the rated capacity P30 of the storage battery unit 30.
According to the configuration of the storage battery system control device 100_2, it is possible to improve the operation rate of the storage battery unit 20, and further, as it is possible to reduce the number of charge / discharge times of the storage battery 304 of the storage battery unit 30, an extended service life of the storage battery 304 can be expected.
Hereinafter, a control mode of the storage battery system control device 100_2 of the storage battery system 1 according to the present Embodiment 2 will be described.
The output of the fluctuation suppression storage battery system power calculation unit 1100 is output to a power distribution unit 1200 (hereinafter, referred to as a "first power distribution unit") similar to that of Embodiment 1 and a power distribution unit 1300 (hereinafter, referred to as a "second power distribution unit") newly provided in Embodiment 2.
In the second power distribution unit 1300, multipliers 1301 and 1302 multiply the outputs of the fluctuation suppression storage battery system power calculation unit 1100 by the respective rated capacity ratios of the storage battery units 20 and 30, and limit each product to within the dischargeable power and the chargeable power at limiters 1303 and 1304.
The output power command value of the storage battery unit 20 calculated by the limiter 1014 of the first power distribution unit 1200 and the output power command value of the storage battery unit 20 calculated by the limiter 1304 of the

second power distribution unit 1300 are input to the calendar function switcher 1400. In periods during which the output of the solar power generation system 40 is anticipated to be greater than the first predetermined value, the output power command value input from the first power distribution unit 1200 is output as the output power command value P_Refl for use by the storage battery unit 20 to suppress the output change rate of the solar power generation plant 600. In periods other than the above described period, the output of the limiter 1304 is output as the output power command value P_Refl for use by the storage battery unit 20 to suppress the output change rate of the solar power generation plant 600.
Similarly, the output power command value of the storage battery unit 30 calculated by the limiter 1012 of the first power distribution unit 1200 and the output power command value of the storage battery unit 30 calculated by the limiter 1303 of the second power distribution unit 1300 are input to the calendar function switcher 1400. In periods during which the output of the solar power generation system 40 is anticipated to be greater than the first predetermined value, the output power command value input from the first power distribution unit 1200 is output as the output power command value P_Ref2 for use by the storage battery unit 30 to suppress the output change rate of the solar power generation plant 600. In periods other than the above described period, the output of the limiter 1303 is output as the output power command value P_Ref2 for use by the storage battery unit 30 to suppress the output change rate of the solar power generation plant 600.
As described above, according to the present Embodiment 2, even in cases in which the output of the solar power generation system 40 suddenly decreases, the output change rate of the solar power generation plant 600 can be suppressed by discharging from the storage battery unit 20, and it is impossible to improve the compliance rate with respect to the fluctuation suppression request.
In addition, by performing power distribution control that causes the storage battery 20 to perform standby with a high charging rate, even in cases in which the dischargeable power of the storage battery unit 30 that suppresses the output fluctuation of the solar power generation system 40 during normal operation decreases, the likelihood increases that the storage battery unit 20 can perform discharging to limit the output change rate of the solar power generation plant 600 within a predetermined range.

Furthermore, according to the present Embodiment 2, since it is possible to use the power storage unit 20 to suppress output fluctuation of the solar power generation plant 600 in periods in which it is anticipated that the output of the solar power generation system 40 will be lower than the first predetermined value, an extended service life of the storage battery 304 can be expected.

WE CLAIMS

1.A storage battery system configured to connect to a connection point between a
power generation source and an electric power system, the storage battery system
comprising:
a plurality of storage battery units! and
a storage battery system control device configured to calculate output power command values of the plurality of storage battery units and control the plurality of storage battery units,
wherein the storage battery system control device is configured to suppress an output change rate of the power generation source by:
setting, in a case that an output fluctuation of active power output by the power generation source toward the electric power system is within a predetermined range, an output power command value for a first storage battery unit from among the plurality of storage battery units to a value with an absolute value that is smaller than an output power command value for another storage battery unit among the plurality of storage battery units, and
setting, in a case that the output fluctuation of active power exceeds the predetermined range, an output power command value for the first storage battery unit to a value that increases charging and discharging from the first storage battery unit, and operating in a first control mode configured to compensate for an insufficient power amount due to charging and discharging from the another storage battery unit.
2. The storage battery system according to Claim 1, wherein:
the storage battery system control device includes a second control mode in which output power command values for each of the plurality of storage battery units are allocated based on a ratio between a rated capacity of the first storage battery unit and a rated capacity of the another storage battery unit, and is configured to suppress an output change rate of the power generation source by switching between the first control mode and the second control mode based on a time period.

3. The storage battery system according to either Claim 1 or Claim 2, wherein:
an upper limit value of the predetermined range is set as a dischargeable electric power of the other storage battery unit, and a lower limit value of the predetermined range is set as chargeable electric power of the other storage battery unit.
4. The storage battery system according to any one of Claim 1 to Claim 3,
wherein:
the storage battery system control device is configured to calculate the output power command values based on a power amount of the active power that exceeds a difference between an output upper limit value and an output lower limit value of the active power.
5. The storage battery system according to any one of Claim 1 to Claim 3,
wherein:
the storage battery system control device is configured to calculate the output power command values from an electric power amount obtained by performing high-pass filter operation processing on an output active power detection value of the power generation source.
6. The storage battery system according to any one of Claim 1 to Claim 5,
wherein:
the storage battery system control device prepares, for the first storage battery unit, a plurality of charge rate command values to be instructed in advance, and switches the plurality of charge rate command values as inputs.
7. The storage battery system according to any one of Claim 1 to Claim 6,
wherein:
the power generation source is a power source based on renewable energy.
8. The storage battery system according to Claim 7, wherein:
the power source based on the renewable energy is a solar power generation system.

9. The storage battery system according to Claim 7, wherein:
the power source based on the renewable energy is a wind power generation system.
10. A control method for a storage battery system configured to connect to a
connection point between a power generation source and an electric power system,
wherein, when calculating output power command values of a plurality of storage
battery units provided in the storage battery system and controlling the plurality of
storage battery units, the control method comprises:
a first step of setting, in a case that an output fluctuation of active power output by the power generation source toward the electric power system is within a predetermined range, an output power command value for a first storage battery unit from among the plurality of storage battery units to a value with an absolute value that is smaller than an output power command value for another storage battery unit among the plurality of storage battery units! and
a second step of setting, in a case that the output fluctuation of active power exceeds the predetermined range, an output power command value for the first storage battery unit to a value that increases charging and discharging from the first storage battery unit, and suppressing an output change rate of the power generation source by compensating for an insufficient power amount due to charging and discharging from the another storage battery unit.
11. The control method for the storage battery system according to Claim 10,
further comprising:
a third step in which output power command values for each of the plurality of storage battery units are allocated based on a ratio between a rated capacity of the first storage battery unit and a rated capacity of the another storage battery unit; and
wherein an output change rate of the power generation source is suppressed by switching between a control of the first and second steps and a control of the third step based on a time period.

12. The control method for the storage battery system according to either Claim 10
or Claim 11, wherein:
the output power command values are calculated based on a power amount of the active power that exceeds a difference between an output upper limit value and an output lower limit value of the active power.
13. The control method for the storage battery system according to either Claim 10
or Claim 11, wherein:
The output power command values are calculated from an electric power amount obtained by performing high-pass filter operation processing based on an output of the active power.