JP2015213409A - Load leveling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a load leveling device, capable of efficiently suppressing the variation of a system frequency, without damaging a load leveling function of a consumer.SOLUTION: A load leveling device 30, which is installed at a consumer 20 of an electric power system 1 and includes a secondary battery 32 capable of charging and discharging to thereby perform the load leveling of an electricity demand, further includes: system frequency detection means 33 for detecting a system power frequency; and control means 34 for controlling the charge or discharge of the secondary battery 32. The control means 34 charges the secondary battery 32 in a first time zone, in which power used by the consumer 20 is small, and when the system frequency exceeds a predetermined threshold.

Description

  The present invention relates to a load leveling device that performs load leveling of power demand using a secondary battery installed in a consumer.

  In general, power consumption tends to be small at night and increased during the day. Especially in the summer, which is the peak season, the amount of power demand during the daytime hours is higher than during periods other than the peak season (see FIGS. 17 and 18). In order to eliminate such a difference in the amount of power demand between day and night, load leveling of power demand is performed. Load leveling uses, for example, a rechargeable battery that can be charged and discharged, and is charged at night when the amount of power used is low, and discharged during the day to reduce the amount of power during the day. It is to reduce (peak cut).

  In recent years, power generation facilities using renewable energy such as wind power generation and solar power generation are increasing. However, in such wind power generation and solar power generation, power output fluctuations remarkably occur depending on the strength of wind and the state of sunlight due to clouds, so it is difficult to stably supply power. For this reason, there is a concern about the influence of such power fluctuations on system power and distribution line voltage. On the other hand, it is known that when the balance between the power supply amount and the demand amount is lost, the frequency of the system power (hereinafter referred to as the system frequency) fluctuates.

  Conventionally, power output fluctuations and system frequency fluctuations have been dealt with by controlling the output by a generator such as thermal power generation, but there is a limit to these correspondences, and for the part that can not be dealt with, The use of secondary batteries such as storage batteries has been proposed. However, since the secondary battery is expensive, it is not practical for a system company such as an electric power company to install it in all facilities because the burden is large. On the other hand, in power system consumers, secondary batteries are beginning to be installed in factories, office buildings and the like for load leveling of power demand. In addition, it has been proposed to use a secondary battery intended for load leveling in order to adjust the system frequency (Patent Document 1).

JP 2012-205462 A

  In Patent Document 1, in a preset base charge / discharge pattern, the adjusted charge / discharge power adjusted by the change in frequency is added to the charge / discharge power serving as the base to add to the storage battery (secondary battery). The discharge charge is controlled. Thereby, the fluctuation | variation of the system frequency is suppressed, without preventing the load leveling by a storage battery.

  By the way, it is known that the relationship between the balance between the power demand and the power supply and the system frequency is that the system frequency decreases when the demand exceeds the supply, and the system frequency increases when the demand falls below the supply. . In the charging / discharging control in Patent Document 1, since charging / discharging is performed according to a preset base charging / discharging pattern, even when the system frequency is lowered, that is, even when the demand for power exceeds the supply, the charge amount However, the battery is continuously charged. For this reason, since the amount of power demand does not greatly decrease, fluctuations in the system frequency cannot be efficiently suppressed.

  In view of the above circumstances, the technical problem to be solved by the present invention is to provide a load leveling device that can efficiently suppress fluctuations in the system frequency without impairing the load leveling function of the consumer. There is to do.

  In order to solve the above problems, a load leveling apparatus according to the present invention has a secondary battery that can be charged and discharged and installed at a consumer of an electric power system. A load leveling device that performs load leveling, and includes a system frequency detection unit that detects a frequency of system power, and a control unit that controls charging or discharging of a secondary battery. The secondary battery is charged when the power consumption is in the first time zone with less power consumption and the system frequency exceeds a predetermined threshold.

  By configuring in this way, the system frequency is charged in order to charge the secondary battery when the system frequency is higher than a predetermined threshold in the first time zone where power consumption is low, such as at night. Is high, that is, by charging in a state where the demand is lower than the supply, the demand for electric power can be increased. As a result, the system frequency can be lowered. Further, when the system frequency becomes lower than a predetermined threshold, charging of the secondary battery is stopped, so that the demand for power can be reduced. Thereby, the fall of the system frequency is suppressed. In this way, it is possible to eliminate an imbalance between the demand and supply of power, and to efficiently suppress fluctuations in the system frequency.

  At this time, the secondary battery is intermittently charged in order to perform charging when the system frequency exceeds a predetermined threshold. Here, the secondary battery can use the recovery voltage by charging intermittently, and can charge more power than charging continuously. Therefore, the charge leveling function using the secondary battery can be improved by charging a large amount of power.

  Moreover, it is preferable to make constant the electric power charged to a secondary battery irrespective of a system | strain frequency. Electric power for charging the secondary battery is converted from AC to DC and charged. Here, the converter for converting from alternating current to direct current has a power value with good conversion efficiency, and the conversion is preferably performed with a value with good conversion efficiency. Thus, the secondary battery can be efficiently charged by charging with a constant power value with good conversion efficiency.

  Furthermore, the power charged in the secondary battery may be changed in proportion to the system frequency. That is, the charging power is increased when the difference between the system frequency and the predetermined threshold is large, and the charging power is decreased when the difference between the system frequency and the predetermined threshold is small. Thereby, when the difference between the system frequency and the predetermined threshold value is large, the demand amount of power increases by increasing the charging power, so that the system frequency can be greatly decreased. On the other hand, when the difference between the system frequency and the predetermined threshold is small, by reducing the charging power, the power demand is not so large compared to the above, and the system frequency can be lowered gradually. As described above, by changing the power charged in the secondary battery in proportion to the system frequency, it is possible to efficiently suppress fluctuations in the system frequency.

  Moreover, you may change the electric power charged to a secondary battery in steps according to a system | strain frequency. Thereby, in addition to increasing / decreasing the charging power depending on the difference between the system frequency and the predetermined threshold, the charging power at the predetermined system frequency can be appropriately increased / decreased. Here, in order to efficiently suppress fluctuations in the system frequency by charging the secondary battery, charging the secondary battery over the entire period from the beginning to the end time of the first time zone. Preferably it is done. Therefore, the amount of charge can be controlled so that charging to the secondary battery is not completed during the first time period by increasing or decreasing the charging power at a predetermined frequency according to the amount of charge of the secondary battery. it can. In addition, since charging power is increased / decreased according to a system frequency, the fluctuation | variation of a system frequency can also be suppressed efficiently like the above.

  Further, the control means determines whether or not the state of charge of the secondary battery has reached a predetermined reference value every predetermined time in the first time zone, and determines that the predetermined reference value has been reached. May increase the threshold by a predetermined amount and maintain the threshold when it is determined that the predetermined reference value has not been reached. For example, when the state where the system frequency is higher than a predetermined threshold continues, the secondary battery is continuously charged. For this reason, the charging of the secondary battery may be completed in the initial stage or in the middle of the first time period for charging. Then, at the end of the first time zone, it becomes impossible to suppress fluctuations in the system frequency due to charging of the secondary battery. Therefore, it is confirmed whether or not the state of charge of the secondary battery has reached a predetermined reference value every predetermined time. If the amount of charge has reached the predetermined reference value within the predetermined time, the threshold value for charging is set. By making it rise, it makes charging difficult. Thereby, in a 1st time slot | zone, charging is not completed early, but it can charge over time. As a result, it is possible to efficiently suppress fluctuations in the system frequency due to charging of the secondary battery. In addition, when the charging state of the secondary battery does not reach the predetermined reference value, the charging can be continuously performed under the same conditions by maintaining the threshold value.

  Further, the control means determines whether or not the state of charge of the secondary battery has reached a predetermined reference value every predetermined time in the first time zone, and determines that the predetermined reference value has been reached. May increase the threshold by a predetermined amount, and decrease the threshold by a predetermined amount when it is determined that the predetermined reference value has not been reached. For example, contrary to the above, if the system frequency continues to be lower than a predetermined threshold, the secondary battery is not charged much. Therefore, in the initial stage of the first time zone in which charging is performed, if the secondary battery is not charged much, there is a possibility that the charging will not be completed within the first time zone. Therefore, it is confirmed whether or not the state of charge of the secondary battery has reached a predetermined reference value every predetermined time, and if the charge amount has not reached the predetermined reference value within the predetermined time, the threshold value for charging is set. Lowering makes it easier to charge. As a result, the charging of the secondary battery can be completed with certainty. If the amount of charge has reached a predetermined reference value within a predetermined time, as in the above case, the threshold value is increased to prevent early completion of charging and the system frequency due to charging of the secondary battery. This effectively suppresses fluctuations.

  Further, the first time zone is set longer than the charging time required to charge the target charge amount to the secondary battery, and the control means sets the charge amount and the target charged to the secondary battery at a predetermined time point. The remaining charge until the charge is completed is calculated from the charge amount, and the remaining charge time required to charge the remaining charge is determined based on the relationship between the charge amount of the secondary battery and the charge time obtained in advance. Compare the remaining time from the predetermined time to the end of the first time period with the remaining charge time.If the remaining time matches the remaining charge time, the secondary battery is continuously charged during the remaining time. You may go. Here, since the system frequency fluctuates irregularly and uncertainly, if it often falls below a predetermined threshold, charging may not be completed when the first time period ends. Therefore, the relationship between the amount of charge to the secondary battery and the charging time is obtained in advance, and the remaining time from the predetermined time until the end of the first time zone is compared with the remaining charging time until the charging is completed. When the remaining time matches the remaining charging time, the remaining time is continuously charged. Thereby, at the end of the first time zone, the charging of the secondary battery can be reliably completed.

  On the other hand, in order to solve the above-mentioned problem, a load leveling device according to the present invention has a secondary battery that can be charged and discharged and installed in a power system consumer. A load leveling device that performs load leveling of demand, comprising system frequency detection means for detecting the frequency of system power, and control means for controlling charging or discharging of the secondary battery. The secondary battery is discharged when it is in the second time zone where the power consumed by the house is large and the system frequency falls below a predetermined threshold.

  By configuring in this way, for example, in order to discharge from the secondary battery in the second time zone where there is a large amount of power used, such as daytime, and when the system frequency falls below a predetermined threshold, the system frequency Is low, that is, by discharging in a state where the supply is less than the demand, the supply of power can be increased. As a result, the system frequency can be increased. Further, when the system frequency becomes higher than a predetermined threshold value, the discharge from the secondary battery is stopped, so that the power supply can be reduced. Thereby, an increase in the system frequency is suppressed. In this way, it is possible to eliminate an imbalance between the demand and supply of power, and to efficiently suppress fluctuations in the system frequency.

  At this time, since the discharge is performed when the system frequency falls below a predetermined threshold, the secondary battery is intermittently discharged. Here, the secondary battery can use the recovery voltage by discharging intermittently, and can discharge more power than continuous discharge. Therefore, by discharging a large amount of power, the load leveling function using the secondary battery can be improved.

  Moreover, it is preferable to make the electric power discharged by the secondary battery constant regardless of the system frequency. The electric power discharged from the secondary battery is converted from direct current to alternating current and discharged. Here, the converter for converting from direct current to alternating current has a power value with good conversion efficiency, and the conversion is preferably performed with a value with good conversion efficiency. Thus, the secondary battery can be efficiently discharged by discharging at a constant power value with good conversion efficiency.

  Furthermore, the electric power discharged from the secondary battery may be changed in proportion to the system frequency. That is, when the difference between the system frequency and the predetermined threshold is large, the discharge power is increased, and when the difference between the system frequency and the predetermined threshold is small, the discharge power is decreased. Thereby, when the difference between the system frequency and the predetermined threshold is large, the supply amount of power is increased by increasing the discharge power, so that the system frequency can be greatly increased. On the other hand, when the difference between the system frequency and the predetermined threshold is small, by reducing the discharge power, the amount of power supply is not so large as compared to the above, and the system frequency can be increased gradually. In this way, by changing the power discharged from the secondary battery in proportion to the system frequency, it is possible to efficiently suppress fluctuations in the system frequency.

  Moreover, you may change the electric power which a secondary battery discharges in steps according to a system | strain frequency. Thereby, in addition to increasing / decreasing the discharge power depending on the difference between the system frequency and the predetermined threshold, the discharge power at the predetermined system frequency can be appropriately increased / decreased. Here, in order to efficiently suppress fluctuations in the system frequency by the discharge from the secondary battery, the discharge from the secondary battery is performed over the entire period from the beginning to the end time of the second time zone. Preferably it is done. Therefore, it is possible to control the discharge amount so that the discharge from the secondary battery is not completed in the middle of the second time period by increasing or decreasing the discharge power at a predetermined frequency according to the discharge amount of the secondary battery. it can. In addition, since discharge electric power is increased / decreased according to a system frequency, the fluctuation | variation of a system frequency can also be suppressed efficiently like the above.

  Further, the control means determines whether or not the discharge state of the secondary battery has reached a predetermined reference value every predetermined time in the second time zone, and determines that the predetermined reference value has been reached. May lower the threshold by a predetermined amount and maintain the threshold when it is determined that the predetermined reference value has not been reached. For example, when the state where the system frequency is lower than a predetermined threshold continues, the secondary battery is continuously discharged. Therefore, the discharge from the secondary battery may be completed in the initial stage or in the middle of the second time period during which the discharge is performed. Then, at the end of the second time zone, it becomes impossible to suppress the fluctuation of the system frequency due to the discharge from the secondary battery. Therefore, it is confirmed whether the discharge state of the secondary battery has reached a predetermined reference value every predetermined time. If the discharge amount has reached the predetermined reference value within the predetermined time, the threshold value for discharging is set. Lowering makes it difficult to discharge. Thereby, in the second time zone, the discharge is not completed at an early stage, and the discharge can be performed over time. As a result, the fluctuation of the system frequency due to the discharge from the secondary battery can be efficiently suppressed. When the discharge state of the secondary battery does not reach the predetermined reference value, the discharge can be continuously performed under the same conditions by maintaining the threshold value.

  Further, the control means determines whether or not the discharge state of the secondary battery has reached a predetermined reference value every predetermined time in the second time zone, and determines that the predetermined reference value has been reached. May decrease the threshold by a predetermined amount, and increase the threshold by a predetermined amount when it is determined that the predetermined reference value has not been reached. For example, contrary to the above, when the system frequency continues to be higher than a predetermined threshold, the secondary battery is not discharged so much. Therefore, when the secondary battery is not discharged so much in the initial stage of the second time period when the discharge is performed, there is a possibility that the discharge is not completed within the second time period. Therefore, it is confirmed whether or not the discharge state of the secondary battery reaches a predetermined reference value every predetermined time. If the discharge amount does not reach the predetermined reference value within the predetermined time, the threshold value for discharging is set. Increasing it makes it easier for discharge to occur. As a result, the discharge from the secondary battery can be completed with certainty. In addition, when the discharge amount reaches a predetermined reference value within a predetermined time, the completion of early discharge is prevented by lowering the threshold value in the same manner as described above, and the system frequency due to discharge from the secondary battery is reduced. This effectively suppresses fluctuations.

  Further, the second time zone is set longer than the discharge time required to discharge the target discharge amount from the secondary battery, and the control means sets the discharge amount discharged from the secondary battery at the predetermined time point and the target amount. The remaining amount of discharge until the discharge is completed is determined from the discharge amount, and the remaining discharge time required to discharge the remaining discharge amount is determined based on the relationship between the discharge amount of the secondary battery and the discharge time obtained in advance. Compare the remaining time from the predetermined time to the end of the second time period with the remaining discharge time, and if the remaining time matches the remaining discharge time, the secondary battery is continuously discharged from the remaining time. You may go. Here, since the system frequency fluctuates irregularly and uncertainly, if it often exceeds a predetermined threshold value, there is a possibility that the discharge will not be completed when the second time period ends. Therefore, the relationship between the amount of discharge from the secondary battery and the discharge time is obtained in advance, and the remaining time from the predetermined time until the end of the second time zone is compared with the remaining discharge time until the discharge is completed. When the remaining time matches the remaining discharge time, the remaining time is continuously discharged. Thereby, at the end of the second time zone, the discharge from the secondary battery can be reliably completed.

  As described above, according to the present invention, it is possible to provide a load leveling apparatus that can efficiently suppress fluctuations in the system frequency without impairing the load leveling function of the consumer.

It is the schematic which shows the state which connected the load leveling apparatus concerning one Embodiment of this invention to the electric power grid | system. Explanatory drawing which shows the timing of charge of a secondary battery in the load leveling apparatus concerning FIG. Explanatory drawing which shows the relationship between time and the voltage at the time of charge to said secondary battery. Explanatory drawing which shows electric power with favorable conversion efficiency in the converter used for the load leveling apparatus concerning FIG. In said secondary battery, explanatory drawing which shows the relationship between charge remaining charge and charge remaining time. Explanatory drawing which put together the relationship between the time in the load leveling apparatus concerning FIG. 1, a system | strain frequency, charging power, and charge amount. (A)-(c) Explanatory drawing which shows the relationship between a system | strain frequency and charging power in charge to said secondary battery. (A)-(c) Explanatory drawing which shows the relationship between time and the threshold value of a system | strain frequency in charge to said secondary battery. (A)-(c) Explanatory drawing which shows the other example of the relationship between time and the threshold value of a system frequency in charge to said secondary battery. Explanatory drawing which shows the timing of the discharge of a secondary battery in the load leveling apparatus concerning FIG. Explanatory drawing which shows the relationship between time and a voltage in the case of discharge from said secondary battery. In said secondary battery, explanatory drawing which shows the relationship between discharge residual amount and discharge remaining time. Explanatory drawing which put together the relationship between the time in the load leveling apparatus concerning FIG. 1, a system | strain frequency, discharge electric power, and discharge amount. (A)-(c) Explanatory drawing which shows the relationship between a system | strain frequency and discharge electric power in discharge from said secondary battery. (A)-(c) In the discharge from said secondary battery, explanatory drawing which shows the relationship between time and the threshold value of a system | strain frequency. (A)-(c) In the discharge from said secondary battery, explanatory drawing which shows the other example of the relationship between time and the threshold value of a system | strain frequency. Explanatory drawing which shows the example of the conventional load leveling in the peak period. Explanatory drawing which shows the example of the load leveling in the past except the peak period.

  Hereinafter, an embodiment of a load leveling apparatus according to the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram illustrating a state in which a load leveling device according to an embodiment of the present invention is connected to a power system. The power system 1 is an entire facility that performs power generation (power generation) to consumption, and a power generation facility 10 that generates power and a consumer 20 that consumes power are connected via a transmission line 11.

  The power generation facility 10 is a facility owned by a system operator, and generates power by various methods such as thermal power generation, hydropower generation, and nuclear power generation. A power transmission line 11 that transmits the generated power is connected to the power generation facility 10. The power transmission line 11 transmits the power generated by the power generation facility 10 via the substation 12 and the transformer 13. Here, the substation 12 is a facility that converts the voltage and frequency of the power generated by the power generation facility 10, and the transformer 13 is a device that further converts the voltage.

  The power transmission line 11 is connected to other power generation facilities such as a solar power generation 10A and a wind power generation 10B. The solar power generation 10A and the wind power generation 10B are facilities that generate power using renewable energy such as sunlight and wind power. Unlike the power generation facility 10 owned by the grid operator, these facilities are small-scale facilities, and are installed in a factory or an office building.

  The customer 20 is a facility that is connected to the power transmission line 11 to receive and consume power. Hereinafter, in the electric power system 1, electric power consumers who are supplied with electric power, such as large facilities such as factories and buildings, and private homes, are collectively referred to as consumers 20. The consumer 20 is provided with various loads 21 that consume power. In the following, a system with a rating of 100 kW in the customer 20 will be described as an example.

  The load leveling device 30 is installed in the facility of the customer 20. In addition, the load leveling device 30 includes a secondary battery 32 that can be charged and discharged via the converter 31, a system frequency detection unit 33 that detects a frequency (system frequency) of system power, a secondary battery 32, And control means 34 connected to the system frequency detection means 33.

  The converter 31 is a device that mutually converts AC power and DC power, and specifically has a function of a converter that converts AC power to DC power and a function of an inverter that converts DC power to AC power. . In the present embodiment, system power, which is AC power, is converted to DC power to charge the secondary battery 32, and DC power stored in the secondary battery 32 is converted to AC voltage to generate power. Discharge to system 1.

  The secondary battery 32 stores power by charging and supplies power by discharging. For example, a livestock battery with less self-discharge, such as a well-known lithium ion battery or sodium sulfur battery, is preferable. Here, when the secondary battery 32 is charged, a charge amount slightly lower than the full charge is set as the target charge amount for the chargeable capacity, and the target charge is set at the end of the first time zone. Charge to the amount. Further, at the time of discharging, the charged electric power is set to be completely discharged, and discharging is performed so as to be completely discharged at the end of the second time zone.

  The system frequency detection means 33 is a means for detecting the system frequency by a known method. Here, the system frequency is 50 Hz in eastern Japan and 60 Hz in western Japan. In addition, as described above, the system frequency fluctuates depending on the balance between the amount of power demand and supply, and the fluctuation of the system frequency increases or decreases in a minute cycle of several minutes and a large cycle of several tens of minutes. . Note that the system operator controls the fluctuation range of the system frequency to be within ± 0.1 Hz, for example, by adjusting the amount of power generated by the power generation facility 10. Further, as shown in FIG. 1, the system frequency detection unit 33 may acquire system frequency information directly from the system operator 40.

  The control means 34 is connected to the secondary battery 32 and the system frequency detection means 33. The control unit 34 switches between charging and discharging of the secondary battery 32 based on time information acquired by a clock (not shown). Further, based on the value of the system frequency detected by the system frequency detection means 33, the timing of charging or discharging the secondary battery 32 is controlled. As described above, the control unit 34 performs various controls on the load leveling device 30. Details of control of charging or discharging the secondary battery 32 by the control unit 34 will be described later.

  Next, the operation of the load leveling device 30 will be described. The load leveling device 30 charges the secondary battery 32 at night as a first time zone where the power consumption is low, and the secondary battery 32 during the daytime as a second time zone when the power usage is high. By performing discharge from the power source, load leveling of power demand is performed. In the present embodiment, the first time zone is from 10 pm (22:00) to 8 am, and the second time zone is from 8 am to 10 pm. Note that, as described above, switching between discharging and charging of the secondary battery 32 is performed by the control means 34.

  Hereinafter, the details of the control of charging the secondary battery 32 in the first time zone performed by the control unit 34 will be described. FIG. 2 shows the relationship between the time of the first time zone and the system frequency, and the charging timing of the secondary battery 32. Here, the system frequency is controlled by the system operator so as to be within ± 0.1 Hz with respect to 60 Hz in Western Japan. The system frequency fluctuates irregularly, and the fluctuation of the system frequency shown in FIG. 2 shows an example.

  The secondary battery 32 is charged when the system frequency exceeds a predetermined threshold as shown in FIG. In the present embodiment, the predetermined threshold is 60 Hz. The system frequency detection unit 33 detects the system frequency and transmits the detected value to the control unit 34. The control unit 34 charges the secondary battery 32 when the system frequency exceeds a predetermined threshold value (60 Hz) set in advance, and stops charging the secondary battery 32 when the system frequency falls below the predetermined threshold value. Thus, since the secondary battery 32 is charged when the system frequency exceeds a predetermined threshold, the power demand in the power system 1 increases. Therefore, the system frequency can be lowered.

  As shown in FIG. 2, in the first time zone (22:00 to 8:00), the system frequency exceeds a predetermined threshold in the time zone from 22:00 to time a and from time b to time c. The secondary battery 32 is charged. In addition, after time d, charging is performed even in a state where the system frequency is below the threshold value, but details will be described later.

  Thus, since the secondary battery 32 is charged when the system frequency exceeds a predetermined threshold, the secondary battery 32 is intermittently charged. FIG. 3 shows the relationship between time and voltage when the secondary battery 32 is charged. As illustrated, the charging of the secondary battery 32 is intermittently performed until the voltage reaches a predetermined value (predetermined voltage). Here, the voltage rises while the secondary battery 32 is charged. On the other hand, while the battery is not charged, the voltage of the secondary battery 32 decreases. This is called the recovery voltage. The voltage measured during charging is a value measured including the internal resistance, and the voltage increases by the amount of the internal resistance. However, since the measured value during the charge stop does not include the internal resistance, a substantial voltage of the secondary battery 32 is indicated. Therefore, if the secondary battery 32 is intermittently charged, the recovery voltage can be used as compared with the case where the secondary battery 32 is continuously charged. Therefore, the amount of power that can be charged in the secondary battery 32 can be increased.

  Further, since the system power is alternating current, it is converted into direct current by the converter 31 (see FIG. 1) and charged to the secondary battery 32. Here, as shown in FIG. 4, the converter 31 has a range of electric power with good conversion efficiency. For example, if the rating (upper limit) of the converter 31 is 100 kW, the conversion efficiency is good at 60 kW to 100 kW. In the present embodiment, AC system power is converted to 80 kW using a converter 31 with a rating of 100 kW. As a result, the secondary battery 32 is charged with 80 kW of DC power.

  Here, charging after time d in FIG. 2 will be described. As described above, when the secondary battery 32 is charged when the system frequency exceeds a predetermined threshold, the fluctuation of the system frequency is irregular and uncertain, so the time when the system frequency exceeds the predetermined threshold. If the amount is small, the charging time cannot be sufficiently taken, and there is a possibility that the charging will not be completed before the first time period ends. Therefore, the control unit 34 performs control so that the secondary battery 32 is continuously charged when the end time of the first time zone approaches. Note that the first time zone is set longer than the charging time required to charge the secondary battery 32 with the target charge amount.

  The control of the control means 34 when the end time of the first time zone is near will be described in detail below. First, the remaining amount until the charging is completed (hereinafter referred to as the remaining charge amount) is obtained from the amount of charge charged in the secondary battery 32 at a predetermined time and the target amount of charge. Further, the relationship between the amount of charge to the secondary battery 32 and the charging time is obtained in advance. From this relationship, the time required to charge the remaining charge (hereinafter referred to as remaining charge time) is obtained. Furthermore, when the remaining time from the predetermined time point until the end of the first time period is compared with the remaining charge time and the remaining time matches the remaining charge time, the remaining time The battery 32 is continuously charged.

  FIG. 5 shows the relationship between the remaining charge of the secondary battery 32 and the remaining charge time. This relationship is the same as the relationship between the charge amount and the charge time, and indicates the charge time until the target charge amount is reached from the predetermined charge amount. Here, if the vertical axis corresponds to the time of the first time zone in which the secondary battery 32 is charged, the point indicating the predetermined time and the remaining charge at that time is in the region above the straight line in the figure. Once located, charging can be completed by the end of the first time period. In this case, since it is not necessary to perform charging continuously, charging is performed by the above control. However, if the point indicating the predetermined time and the remaining charge at that time is located in the area below the straight line in the figure, charging will be completed by the end of the first time zone even if charging is performed thereafter Can not do. Therefore, when the point indicating the predetermined time and the remaining charge amount at that time is located on the straight line in the figure, it is necessary to start charging and continuously charge until charging is completed.

  Here, a to d shown in FIG. 5 indicate time points corresponding to the respective times shown in FIG. At the time point a, the secondary battery 32 is already charged by a predetermined amount, and is not charged between a and b. At this time, charging is not performed between a and b, but since time has elapsed, in FIG. 5, only the remaining charge time decreases between a and b. In addition, the secondary battery 32 is charged between b and c. During charging, both the remaining charge and the remaining charge time decrease in parallel with the straight line shown in the figure.

  Further, at the time point c, the charging of the secondary battery 32 is stopped because the system frequency falls below a predetermined threshold as shown in FIG. Thereafter, the remaining charge time decreases with the remaining charge remaining at time c (see FIG. 2). As time elapses, it overlaps with the straight line shown in FIG. 5 (indicated by d in FIG. 5). As described above, due to the relationship between the remaining charge time and the remaining charge shown in FIG. 5, it is necessary to continuously charge after the time point d. Therefore, the control means 34 starts charging the secondary battery 32 at the time point d. Further, after this, charging is continuously performed until charging is completed without performing charging control based on the system frequency. By controlling in this way, the charging of the secondary battery 32 can be reliably completed at the end of the first time period. Note that the relationship between the amount of charge and the charging time in the secondary battery 32 (see FIG. 5) changes depending on the change over time of the secondary battery 32, and therefore is updated to the latest information by appropriately measuring.

  For charging the secondary battery 32 performed as described above, various controls by the control means 34, changes in the charge amount, and the like are collectively shown in FIG. Specifically, FIG. 6 shows a relationship between the time of the first time zone, the system frequency, the charging power, and the charging amount. As described above, the rechargeable battery 32 is charged when the system frequency exceeds a predetermined threshold (60 Hz) (until time a and times b to c). The charging power at this time is 80 kW. At this time, the charge amount gradually increases until the target charge amount is reached. Furthermore, when the remaining time in the first time period decreases (time d), charging is started and charging is continued even if the system frequency is below a predetermined threshold. In this way, it is possible to efficiently charge the secondary battery 32 in the first time zone.

  In the above embodiment, the charging power is set to 80 kW and a constant value as shown in FIG. 7A. However, the present invention is not limited to this. For example, the power for charging the secondary battery 32 may be changed in proportion to the system frequency. As shown in FIG.7 (b), with respect to the system frequency of 60 Hz-60.1 Hz, charging power can be changed within the range with a sufficient conversion efficiency of the converter 31 (60 kW-100 kW: refer FIG. 4). preferable. As a result, when the difference between the system frequency and the predetermined threshold is large, the charging power increases, so that the amount of power demand in the power system increases, and the system frequency decreases. On the other hand, when the difference between the system frequency and the predetermined threshold is small, the charging power is small. In this case, since the demand amount of electric power is not so large as compared with the above, the system frequency can be gradually lowered without drastically lowering the system frequency. Thus, by changing the power charged in the secondary battery 32 in proportion to the system frequency, fluctuations in the system frequency can be efficiently suppressed.

  Moreover, you may change the electric power which charges the secondary battery 32 in steps according to a system | strain frequency. The relationship between the system frequency and the charging power in this case is shown in FIG. Thereby, the charging power in a predetermined system frequency can be increased / decreased suitably. In the drawing, in the system frequency where the charging power extends in the vertical direction, the charging power can be appropriately increased or decreased even at the same system frequency. Thus, the charging amount is increased or decreased in consideration of the remaining amount of charge of the secondary battery 32 and the remaining time of the first time zone, thereby reliably completing the charging within the first time zone. Can do. For example, when the charging amount is small with respect to the remaining time, charging can be performed quickly by increasing the charging power at a predetermined system frequency. When the charging amount is large with respect to the remaining time, the charging time can be extended by reducing the charging power at a predetermined system frequency and performing charging. In this example as well, since the amount of charge to the secondary battery 32 is increased or decreased according to the system frequency, it is possible to efficiently suppress fluctuations in the system frequency as described above.

  Furthermore, in the above embodiment, the threshold of the system frequency when charging the secondary battery 32 is 60 Hz, but the present invention is not limited to this. The threshold value of the system frequency may be changed according to the state of charge of the secondary battery 32 every predetermined time. In the present embodiment, the state of charge of the secondary battery 32 is detected every hour to determine whether or not a predetermined reference value (10%) has been reached. As shown in FIG. 8A, from 22:00 to 23:00, charging is performed when the threshold of the system frequency is set to 60 Hz and the threshold is exceeded. When one hour has passed, it is determined whether or not the charge amount of the secondary battery 32 has reached 10%. If it is determined that the charging amount has been reached, the control means 34 performs the next one hour (23:00 to 24:00). Sets the threshold to 60.01 Hz (see FIG. 8B). Similarly, after 1 hour, it is determined whether or not the charge amount of the secondary battery 32 has reached 20%. If it has reached, the threshold value is set to 60.02 Hz, and the same is repeated thereafter. If the threshold of the system frequency is continuously increased every hour, the threshold at the time of 7 o'clock is set to 60.09 Hz at the maximum (see FIG. 8C). On the other hand, if the amount of charge of the secondary battery 32 does not reach the predetermined reference value after 1 hour has elapsed, the set system frequency threshold is maintained as it is.

  In this way, when the amount of charge of the secondary battery 32 has reached a predetermined reference value after a predetermined time has elapsed, the threshold frequency is increased by a predetermined amount, so that the system frequency exceeds the predetermined threshold value. Even when the operation continues, charging can be prevented from being completed in the middle of the first time period. If the charging of the secondary battery 32 is completed in the middle of the first time period, the system frequency fluctuation due to the charging of the secondary battery 32 cannot be controlled thereafter. Therefore, by preventing the charging from being completed in the middle of the first time zone, it is possible to efficiently suppress the fluctuation of the system frequency due to the charging of the secondary battery 32.

  In addition, when a predetermined amount of time has elapsed and the charge amount of the secondary battery 32 has not reached a predetermined value, the threshold value of the system frequency may be decreased. In this case, as shown in FIG. 9A, the system frequency threshold is set to 60.05 Hz from 22:00 to 23:00. After one hour has passed, it is determined whether the amount of charge of the secondary battery 32 has reached 10%. If it is determined that it has reached, the threshold value is increased to 60.06 Hz as described above. If it is determined that it is not, the threshold value is lowered to 60.04 Hz (see FIG. 9B). The same determination and threshold setting are repeated every hour, but at this time, the upper limit of the system frequency is made not to exceed 60.1 Hz, and the lower limit of the system frequency is made not to drop below 60 Hz. For example, when the amount of charge to the secondary battery 32 is large, it becomes 60.09 Hz at the time of 7 o'clock, and when the amount of charge is small, it becomes 60.01 Hz (see FIG. 9C). Thereby, the charge to the secondary battery 32 can be completed reliably.

  Thus, the amount of charge to the secondary battery 32 in the first time zone can be changed by changing the charging power to the secondary battery 32 and the threshold value of the system frequency at the time of charging. In addition, charging can be performed over the entire first time period, and charging can be completed at the end of the first time period. In addition, in consideration of the relationship between the charging time and the charging amount shown in FIG. 5, when the remaining time until the first time period ends and the remaining charging time coincide with each other, the charging is continuously performed. By using together, charging can be completed more reliably at the end of the first time period.

  Note that the threshold of the system frequency for charging the secondary battery 32 is not limited to the value set above, and can be set as appropriate. In addition, the threshold value is set to a large value (for example, 60.09 Hz) at the beginning of the first time period, and the threshold value is controlled to decrease when the charge amount has not reached the predetermined reference value after the predetermined time has elapsed. May be. Further, when the threshold value is raised or lowered, the amount of change may be changed instead of being changed for every fixed value. As described above, by appropriately changing the threshold values of the charging power and the system frequency, the timing and amount of charging of the secondary battery 32 within the first time zone can be controlled. Thereby, suppression of the change of the system frequency in the electric power consumption at night can be performed efficiently.

  Next, details of the control of the discharge from the secondary battery 32 in the second time zone performed by the control unit 34 will be described. FIG. 10 shows the relationship between the time of the second time zone and the system frequency, and the timing of discharge from the secondary battery 32. The system frequency fluctuates irregularly, and the system frequency fluctuation shown in FIG. 10 shows an example.

  As shown in FIG. 10, the secondary battery 32 is discharged when the system frequency falls below a predetermined threshold value. In the present embodiment, the predetermined threshold is 60 Hz. The system frequency detection unit 33 detects the system frequency and transmits the detected value to the control unit 34. The control means 34 discharges from the secondary battery 32 when the system frequency falls below a predetermined threshold (60 Hz) set in advance, and stops discharging from the secondary battery when it exceeds the predetermined threshold. . Thus, since the secondary battery 32 is discharged when the system frequency falls below a predetermined threshold, the amount of power supplied in the power system 1 increases. Therefore, the system frequency can be increased.

  As shown in FIG. 10, in the second time zone (8:00 to 22:00), the system frequency falls below a predetermined threshold in the time zone from 8:00 to time e and from time f to time g. The secondary battery 32 is discharged. In addition, after time h, discharge is performed even in a state where the system frequency exceeds the threshold value, but details will be described later.

  Thus, since the secondary battery 32 is discharged when the system frequency is lower than the predetermined threshold, the secondary battery 32 is intermittently discharged. FIG. 11 shows the relationship between time and voltage when the secondary battery 32 is discharged. As illustrated, the discharge from the secondary battery 32 is intermittently performed until the voltage reaches a predetermined value (predetermined voltage). Here, the voltage decreases while the secondary battery 32 is discharged. On the other hand, while the battery is not discharged, the voltage of the secondary battery 32 rises. This is called the recovery voltage. The voltage measured during discharge is a value measured including the internal resistance, and the voltage decreases by the amount of the internal resistance. However, since the measured value when the discharge is stopped does not include the internal resistance, a substantial voltage of the secondary battery 32 is indicated. Therefore, when the secondary battery 32 is intermittently discharged, the recovery voltage can be used as compared with the case where the secondary battery 32 is continuously discharged, so that the time until the predetermined voltage is reached becomes longer. Therefore, the amount of power that can be discharged from the secondary battery 32 can be increased.

  Moreover, since the secondary battery 32 is direct current, it is converted into alternating current by the converter 31 (refer FIG. 1), and is discharged to an electric power grid | system. The characteristic of the converter 31 has a range of efficient power as shown in FIG. 4 as described above. In this embodiment, the DC power of the secondary battery 32 is converted to 80 kW using the converter 31 having a rating of 100 kW. As a result, 80 kW of AC power is discharged to the power system 1.

  Here, the discharge after time h in FIG. 10 will be described. As described above, when the secondary battery 32 is discharged when the system frequency falls below a predetermined threshold, the fluctuation of the system frequency is irregular and uncertain, so the time when the system frequency falls below the predetermined threshold When there is little, discharge time cannot fully be taken and there exists a possibility that discharge may not be completed by the end of a 2nd time slot | zone. Therefore, the control unit 34 performs control so that the secondary battery 32 is continuously discharged when the end time of the second time zone approaches. The second time period is set longer than the discharge time necessary for discharging the target discharge amount from the secondary battery 32.

  The control of the control means 34 when the end time of the second time zone is near will be described in detail below. First, the remaining amount until the discharge is completed (hereinafter referred to as the remaining discharge amount) is obtained from the discharge amount discharged from the secondary battery 32 at a predetermined time point and the target discharge amount (complete discharge). Further, the relationship between the discharge amount from the secondary battery 32 and the discharge time is obtained in advance. From this relationship, a time required to discharge the remaining discharge (hereinafter referred to as remaining discharge time) is obtained. Further, the remaining time from the predetermined time point until the end of the second time period is compared with the remaining discharge time. If the remaining time matches the remaining discharge time, the remaining time is The secondary battery 32 is continuously discharged.

  FIG. 12 shows the relationship between the remaining discharge amount of the secondary battery 32 and the remaining discharge time. This relationship is the same as the relationship between the discharge amount and the discharge time, and the discharge time from the predetermined discharge amount until reaching the target discharge amount is shown. Here, when the vertical axis corresponds to the time of the second time zone in which the discharge from the secondary battery 32 is performed, the point indicating the predetermined time and the remaining amount of discharge at that time is a region above the straight line in the figure. If it is located, the discharge can be completed by the end of the second time period. In this case, since the discharge does not have to be performed continuously, the discharge by the above control is performed. However, if the point indicating the predetermined time and the remaining amount of discharge at that time is located in the area below the straight line in the figure, the discharge will be completed by the end of the second time zone even if discharge is performed thereafter Can not do. For this reason, when the point indicating the predetermined time and the remaining amount of discharge at that time is located on the straight line shown in the figure, it is necessary to start discharging and continuously discharge until discharging is completed.

  Here, e to h shown in FIG. 12 indicate time points corresponding to the respective times shown in FIG. At the time point e, the secondary battery 32 is discharged by a predetermined amount, and is not discharged between e and f. At this time, although no discharge is performed between e and f, since time has elapsed, only the remaining discharge time is decreased between e and f in FIG. Further, the secondary battery 32 is discharged between f and g. During discharge, both the remaining amount of discharge and the remaining discharge time decrease in parallel with the straight line shown in the figure.

  Furthermore, at the time point g, the system frequency exceeds a predetermined threshold as shown in FIG. 10, and thus the discharge from the secondary battery 32 is stopped. Thereafter, the remaining discharge time decreases with the amount of discharge at time g (see FIG. 10) remaining unchanged. When the time further elapses, it overlaps with the straight line shown in FIG. 10 (indicated by h in FIG. 5). As described above, due to the relationship between the discharge time and the remaining discharge amount shown in FIG. 10, it is necessary to continuously discharge after the time point h. Therefore, the control means 34 starts discharging from the secondary battery 32 at the time point h. Thereafter, the discharge is continuously performed until the discharge is completed without controlling the discharge by the system frequency. By controlling in this way, the discharge from the secondary battery 32 can be reliably completed at the end of the second time zone. Note that the relationship between the discharge amount and the discharge time in the secondary battery 32 (see FIG. 12) varies depending on the change over time of the secondary battery 32, so that the latest information is updated by appropriately measuring.

  FIG. 13 collectively shows various controls by the control means 34, changes in the discharge amount, etc., regarding the discharge from the secondary battery 32 performed as described above. Specifically, FIG. 13 shows the relationship between the time of the second time zone, the system frequency, the discharge power, and the discharge amount. As described above, the discharge from the secondary battery 32 is performed when the system frequency falls below a predetermined threshold (60 Hz) (until time e, times f to g). The discharge power at this time is 80 kW. At this time, the discharge amount gradually decreases until the target discharge amount is reached. Furthermore, when the remaining time in the second time zone decreases (time h), even if the system frequency exceeds a predetermined threshold, the discharge is started and the discharge is continuously performed. In this way, the secondary battery 32 can be efficiently discharged in the second time zone.

  In the above embodiment, the discharge power is set to 80 kW and a constant value as shown in FIG. 14A. However, the present invention is not limited to this. For example, the power for discharging from the secondary battery 32 may be changed in proportion to the system frequency. As shown in FIG. 14B, the discharge power can be changed within a range where the conversion efficiency of the converter 31 is good (60 kW to 100 kW: see FIG. 4) with respect to the system frequency of 60 Hz to 59.9 Hz. preferable. As a result, when the difference between the system frequency and the predetermined threshold is large, the discharge power is increased, so that the amount of power supplied in the power system is increased and the system frequency is increased. On the other hand, when the difference between the system frequency and the predetermined threshold is small, the discharge power is small. In this case, since the amount of power supply is not so large compared to the above, the system frequency can be gradually increased without increasing the system frequency. In this way, by changing the power discharged from the secondary battery 32 in proportion to the system frequency, fluctuations in the system frequency can be efficiently suppressed.

  Moreover, you may change the electric power which discharges from the secondary battery 32 in steps according to a system | strain frequency. The relationship between the system frequency and the discharge power in this case is shown in FIG. Thereby, the discharge electric power in a predetermined system | strain frequency can be increased / decreased suitably. In the drawing, in the system frequency in which the discharge power extends in the vertical direction, the discharge power can be appropriately increased or decreased even at the same system frequency. As a result, the discharge amount is increased or decreased in consideration of the remaining amount of discharge of the secondary battery 32 and the remaining time of the second time zone, so that the discharge is reliably completed within the second time zone. Can do. For example, when the discharge amount is small with respect to the remaining time, it is possible to discharge quickly by increasing the discharge power at a predetermined system frequency. When the discharge amount is large with respect to the remaining time, the discharge time can be extended by reducing the discharge power at a predetermined system frequency. In this example as well, since the discharge amount from the secondary battery 32 is increased or decreased according to the system frequency, the fluctuation of the system frequency can be efficiently suppressed as described above.

  Furthermore, in the above embodiment, the threshold value of the system frequency when discharging from the secondary battery 32 is 60 Hz, but is not limited thereto. The threshold value of the system frequency may be changed according to the discharge state from the secondary battery 32 every predetermined time. In the present embodiment, the discharge state from the secondary battery 32 is detected every hour to determine whether or not a predetermined reference value (10%) has been reached. As shown in FIG. 15 (a), from 8 o'clock to 9 o'clock, the system frequency threshold is set to 60 Hz, and discharge is performed when the frequency falls below the threshold. When one hour has passed, it is determined whether or not the amount of discharge from the secondary battery 32 has reached 10%. If it is determined that the discharge amount has reached, the control means 34 performs the next one hour (9:00 to 10:00). For, the threshold value is set to 59.99 Hz (see FIG. 15B). After one hour has passed, it is similarly determined whether or not the amount of discharge from the secondary battery 32 has reached 20%. If it has reached, the threshold is set to 59.98 Hz, and thereafter the same is repeated. If the threshold value of the system frequency is continuously lowered every hour, the threshold value is set to 59.91 Hz at the maximum 21 times (see FIG. 15C). On the other hand, if the amount of discharge from the secondary battery 32 does not reach a predetermined reference value after 1 hour has elapsed, the set system frequency threshold is maintained as it is.

  In this way, when the discharge amount from the secondary battery 32 has reached a predetermined value after a predetermined time has elapsed, the threshold value is decreased by a predetermined amount, so that the system frequency continues below the predetermined threshold value. Even in this case, it is possible to prevent the discharge from being completed during the second time period. If the discharge from the secondary battery 32 is completed in the middle of the second time zone, the system frequency fluctuation due to the discharge from the secondary battery 32 cannot be controlled thereafter. Therefore, by preventing the discharge from being completed in the middle of the second time zone, it is possible to efficiently suppress the fluctuation of the system frequency due to the discharge from the secondary battery 32.

  Further, the threshold value of the system frequency may be increased when the discharge amount from the secondary battery 32 does not reach the predetermined value after the predetermined time has elapsed. In this case, as shown in FIG. 16A, from 8 o'clock to 9 o'clock, the system frequency threshold is set to 59.95 Hz. In a state where 1 hour has passed, it is determined whether or not the discharge amount from the secondary battery 32 has reached 10%. If it is determined that the discharge amount has reached, the threshold value is lowered to 59.94 Hz as described above, If it is determined that the threshold has not been reached, the threshold is raised to 59.96 Hz (see FIG. 16B). The same determination and threshold setting are repeated every hour, but at this time, the upper limit of the system frequency is made not to exceed 60 Hz, and the lower limit of the system frequency is made not to drop below 59.9 Hz. For example, when the discharge amount from the secondary battery 32 is large, it becomes 59.91 Hz at the time of 21:00, and when the discharge amount is small, it becomes 59.99 Hz (see FIG. 16C). Thereby, the discharge from the secondary battery can be reliably completed.

  Thus, by changing the discharge power from the secondary battery and the threshold value of the system frequency when discharging, the amount of discharge from the secondary battery 32 in the second time zone can be changed, The discharge can be performed over the entire second time period, and the discharge can be completed at the end of the second time period. In consideration of the relationship between the discharge time and the discharge amount shown in FIG. 12, when the remaining time until the end of the second time zone and the remaining discharge time coincide with each other, the control for continuously discharging is performed. By using in combination, the discharge can be completed more reliably at the end of the second time period.

  Note that the threshold of the system frequency for discharging from the secondary battery 32 is not limited to the value set above, and can be set as appropriate. The threshold value is set to a small value (for example, 59.91 Hz) at the beginning of the second time zone, and is controlled so as to increase the threshold value when the discharge amount has not reached the predetermined reference value after a predetermined time has elapsed. May be. Further, when the threshold value is raised or lowered, the amount of change may be changed instead of being changed for every fixed value. Thus, the timing and amount of discharge from the secondary battery 32 within the second time zone can be controlled by appropriately changing the threshold values of the discharge power and the system frequency. Thereby, suppression of the change of the system frequency in the electric power consumption during the daytime can be efficiently performed.

  The embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention. In addition, you may arrange | position the load leveling apparatus 30 of this invention in the some consumer 20 connected to the power transmission line 11 of the electric power grid | system 1. FIG. Moreover, although the example of the electric power grid | system 1 whose system frequency is 60 Hz was shown, it is the same also with the electric power grid | system 1 of 50 Hz. Furthermore, although the system with a rating of 100 kW in the consumer 20 is shown as an example, a system with a rating of 250 kW, 500 kW, or the like may be used.

DESCRIPTION OF SYMBOLS 1 Electric power system 20 Consumer 30 Load leveling apparatus 32 Secondary battery 33 System frequency detection means 34 Control apparatus

Claims (14)

A load leveling device that has a secondary battery that can be charged and discharged and installed in a power system consumer, and that performs load leveling of power demand by charging and discharging the secondary battery,
System frequency detection means for detecting the frequency of the system power;
Control means for controlling charging or discharging of the secondary battery,
The control means charges the secondary battery in a first time zone in which less power is used by the consumer and when the system frequency exceeds a predetermined threshold. Load leveling device.   The load leveling device according to claim 1, wherein power charged in the secondary battery is constant regardless of the system frequency.   The load leveling device according to claim 1, wherein the power charged in the secondary battery is changed in proportion to the system frequency.   The load leveling apparatus according to claim 1, wherein the power charged in the secondary battery is changed stepwise according to the system frequency.   The control means determines whether or not the state of charge of the secondary battery has reached a predetermined reference value every predetermined time in the first time zone, and determines that the predetermined reference value has been reached. The threshold value is increased by a predetermined amount in the case, and the threshold value is maintained when it is determined that the predetermined reference value has not been reached. Load leveling device.   The control means determines whether or not the state of charge of the secondary battery has reached a predetermined reference value every predetermined time in the first time zone, and determines that the predetermined reference value has been reached. The threshold value is increased by a predetermined amount in the case, and the threshold value is decreased by a predetermined amount when it is determined that the predetermined reference value has not been reached. The load leveling device described in 1. The first time zone is set longer than the charging time required to charge the secondary battery with a target charge amount,
The control means obtains a charge remaining amount until the charging is completed from a charge amount charged to the secondary battery at a predetermined time and the target charge amount, and obtains a charge amount and charge of the secondary battery obtained in advance. Based on the relationship with time, the remaining charge time required to charge the remaining charge is obtained, and the remaining time from the predetermined time point until the end of the first time zone and the remaining charge time are calculated. The comparison, wherein when the remaining time coincides with the remaining charge time, the secondary battery is continuously charged during the remaining time. Load fluctuation leveling device. A load leveling device that has a secondary battery that can be charged and discharged and installed in a power system consumer, and that performs load leveling of power demand by charging and discharging the secondary battery,
System frequency detection means for detecting the frequency of the system power;
Control means for controlling charging or discharging of the secondary battery,
The control means is a load that discharges the secondary battery when it is in a second time zone in which a large amount of power is used by the consumer and the system frequency falls below a predetermined threshold. Leveling device.   The load leveling device according to claim 8, wherein the electric power discharged from the secondary battery is constant regardless of the system frequency.   The load leveling device according to claim 8, wherein the electric power discharged from the secondary battery is changed in proportion to the system frequency.   The load leveling device according to claim 8, wherein the electric power discharged from the secondary battery is changed stepwise according to the system frequency.   The control means determines whether or not the discharge state of the secondary battery has reached a predetermined reference value every predetermined time in the second time zone, and determines that the predetermined reference value has been reached. The threshold value is lowered by a predetermined amount in a case, and the threshold value is maintained when it is determined that the predetermined reference value has not been reached. Load leveling device.   The control means determines whether or not the discharge state of the secondary battery has reached a predetermined reference value every predetermined time in the second time zone, and determines that the predetermined reference value has been reached. The threshold value is lowered by a predetermined amount in the case, and the threshold value is raised by a predetermined amount when it is determined that the predetermined reference value has not been reached. The load leveling device described in 1. The second time zone is set longer than the discharge time necessary to discharge the target discharge amount from the secondary battery,
The control means obtains a remaining amount of discharge until the discharge is completed from a discharge amount discharged from the secondary battery at a predetermined time and the target discharge amount, and calculates the discharge amount and discharge of the secondary battery obtained in advance. Based on the relationship with time, the remaining discharge time required to discharge the remaining discharge is obtained, and the remaining time from the predetermined time point until the end of the second time zone and the remaining discharge time are calculated. 14. The discharge according to claim 8, wherein when the remaining time coincides with the remaining discharge time, the secondary battery is continuously discharged during the remaining time. Load fluctuation leveling device.

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