JP2016049008A - Storage battery system, database and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform maintenance charge on partial storage batteries so as prevent an interruption frequency of a fluctuation mitigating operation from being increased in a storage battery system for the purpose of fluctuation mitigation.SOLUTION: A leveling control part or maintenance charge success rate calculation part 103 includes a function for calculating beforehand a relation between a maintenance charge success rate that is a probability capable of completing the maintenance charge without exceeding an optional limit of remaining storage battery banks when the maintenance charge is to be performed on a part of storage battery banks 101 and mitigation of fluctuation is to be continued by the remaining storage battery banks, and a charge state at a time point in which the maintenance charge is started, and for storing data relating to the relation. The maintenance charge success rate is calculated from wind situation/power generation amount/charge and discharge amount data. When maintenance charge is required, while referring the data relating to the relation, a maintenance charge success rate in such a case is calculated and the maintenance charge success rate is compared with a preset threshold. In the case where a result of the comparison is equal to or smaller than the threshold, it is determined that start of the maintenance charge is reserved.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a storage battery system used for mitigating fluctuations in renewable energy such as wind power generation.

  Since renewable energy such as wind power generation is affected by weather, it is necessary to use fluctuation mitigation means such as a storage battery system.

  In charging / discharging a storage battery system, it is important to prevent deterioration of the storage battery by detecting a state of charge (SOC) or the like.

  In Patent Document 1, in order to suppress voltage and frequency fluctuations in the power system due to fluctuations in the output of the wind power generator, a secondary battery (for fluctuation mitigation use) provided in the system stabilization device is periodically recovered and charged. A control method is disclosed that detects the amount of power fluctuation or the amount of power of a wind power generator, detects the passage of a cycle, and performs recovery charging of a secondary battery while operating an electric facility (wind power generator or the like). . As described in FIG. 1B of this document, it is possible to shorten the time for stopping the electric equipment (such as a wind power generator).

JP 2001-286076 A

  In the technique described in Patent Document 1, a single secondary battery is configured to handle the operation / stop of a wind power generator or the like. For this reason, the operating rate cannot be made 100%, and there is room for improvement in that it is necessary to interrupt the fluctuation relaxation operation.

  In a storage battery system using a lead storage battery or the like for fluctuation mitigation applications such as wind power generation, periodic equal charging is required to prevent variation among multiple cells and reset the current integrated charge state (current integrated SOC). . Similarly, in a lithium ion battery, it is necessary to make the open circuit voltage (OCV) measurable as necessary in order to ensure the measurement accuracy of the SOC. Hereinafter, the charge / discharge current 0 state for equal charge and OCV acquisition is collectively referred to as “maintenance charge”.

  In the case of performing the above maintenance charging, if maintenance charging is performed without stopping the fluctuation mitigation operation with emphasis on the operation rate, an extra storage battery capacity (e.g., an increase in the number of banks of the storage battery, an increase in the capacity of each bank, etc.) is conventionally provided. There was a need. On the other hand, from the viewpoint of reducing power plant construction costs in recent years, there is a request to reduce the proportion of storage batteries in the facility cost. In the above case, it becomes a configuration that does not have a surplus storage battery capacity with respect to the generator output, but even if it does not have this surplus storage battery capacity, it is possible to perform maintenance charging without stopping the fluctuation mitigation operation. Increasing the operating rate and improving the power generation balance is an important issue in securing competitiveness.

  An object of the present invention is to perform maintenance charging on some storage battery banks in a storage battery system having a plurality of storage battery banks for use in fluctuation mitigation so as not to pause fluctuation mitigation operations with high probability.

  The storage battery system of the present invention is a system that alleviates fluctuations in the amount of power transmitted from a generator, and a plurality of storage battery banks that can be independently charged and discharged, a leveling control unit, a maintenance charge success rate calculation unit, The storage battery bank includes a plurality of storage batteries, the leveling control unit includes a charge state calculation unit and a charge / discharge control unit, and the leveling control unit or the maintenance charge success rate calculation unit is the storage battery bank Maintenance charge success rate that is the probability that maintenance charge can be completed without exceeding the operation limit of the remaining storage battery bank when maintenance charge is continued for some and the fluctuation of the remaining battery bank is continued. It has a function to calculate the relationship with the state of charge at the time of starting charging in advance and save the data related to this relationship. The maintenance charge success rate is calculated from the wind condition / power generation amount / charge / discharge amount data, and maintenance charge is performed. When necessary, the maintenance charge success rate at this time is calculated by referring to the data related to the above relationship, and the maintenance charge success rate is compared with a preset threshold value. It is characterized by making a decision to reserve the start.

  According to the present invention, in a storage battery system for fluctuation mitigation use, maintenance charging can be performed on some of the storage battery banks so as not to increase the frequency of interruption of the fluctuation mitigation operation.

It is a schematic diagram which shows the whole structure of a storage battery system. It is a graph which shows the example of the maintenance charge success rate curve with respect to SOC at the time of maintenance charge start. It is a flowchart which shows the example of the preparation process of a maintenance charge success rate curve. It is a graph which shows the example of the process which determines maintenance charge success. It is a flowchart which shows the example of the maintenance charge start determination task. It is a graph which shows the example of the relationship between a maintenance charge success rate and waiting time. It is a graph which shows the example which offsets 1/2 of the average waiting time of the maintenance charge of a fixed period. It is a flowchart which shows the example of the preparation procedure of a maintenance charge success rate map.

  The present invention relates to maintenance of a storage battery system used for mitigating fluctuations in renewable energy such as wind power generation that is affected by weather.

  The storage battery system of the present invention includes means for requesting activation of maintenance charging based on an increase in variation between timers and cells, a plurality of storage battery banks that can be independently charged and discharged, the number of storage battery banks, and the output for each bank. Alternatively, means for holding specifications such as capacity, means for holding specifications such as the number of storage battery banks that require maintenance charging, means for calculating the SOC of the storage battery, and a plurality of storage battery banks while continuing the fluctuation mitigation operation Probability that maintenance charging can be completed without breaking the fluctuation mitigation operation in the remaining storage battery banks that do not perform maintenance charging when maintenance charging is performed on some storage battery banks (hereinafter referred to as maintenance charging success rate) ) For each SOC value at the start of maintenance charge (hereinafter referred to as maintenance charge success rate data), a charge / discharge control unit that commands charge / discharge operations to a plurality of storage battery banks, and maintenance charge Maintenance to determine whether or not to actually start maintenance charging based on the current SOC value, storage battery specifications such as storage battery bank configuration, the number of storage battery banks requiring maintenance charging, and maintenance charging success rate data And a charging start determination unit.

  The maintenance charge success rate data is kept for each storage charge bank configuration, specifications such as the performance of each bank, and maintenance charge mode, such as when maintenance charge is performed for m banks out of n banks. May be.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows the overall configuration of the storage battery system. In this figure, a wind power generator is shown as a renewable energy source, but the renewable energy source is not limited to this.

  In this figure, a wind power generator 110 is connected to an external system 108 such as a power transmission line via a bus 109 and a transformer as appropriate. The electric power generated by the wind power generator 110 is supplied to the external system 108. Although not shown, depending on the type of generator (induction or synchronous), for example, in a synchronous generator, the present invention is similarly applied to a configuration that is linked to the external system 108 via a converter-DC bus-inverter link. it can.

  The wind power generator 110 is connected to the storage battery bank 101 via the converter 102. This corresponds to the fact that the electric power generated by the wind power generator 110 changes greatly with time. When the electric power is large, the battery bank 101 is charged, while when the electric power is low, the electric power is discharged from the battery bank 101. This is because the power sent to the external system 108 is leveled. The capacity of the storage battery bank 101 is, for example, a combined output of the wind power generation system that outputs a value obtained by processing the power generation amount of the wind power generator so as to have a predetermined smoothing characteristic to the external system 108, and excess or deficiency with respect to the combined output described above is transferred to the storage battery. When the general fluctuation mitigation operation compensated by charging / discharging is performed, the capacity does not cause excess or deficiency.

  Here, an example of a general fluctuation mitigation operation is shown.

When the generator output current is I _G and the current output to the external system 108 is I _O , the charge / discharge current I _B of the storage battery is expressed by the following formula (1).

Here, for simplification, it is assumed that the voltage is approximately constant, and only the change in current is shown. Further, the sign of the current is positive when discharging is viewed from the storage battery, and negative is charging when viewed from the storage battery. The current I _O to be output to the external system 108 is a smoothing value of the generator output current I _G, as an example is represented by the following equation (2).

Here, F _11st is a smoothing calculation based on a first-order lag, and a simple example includes a calculation represented by the following mathematical formula (3).

In the equation, T _const is a smoothing time constant. F _l1sto (t−1) is a smooth value one _hour before. The above mathematical formula (3) shows the case of a sampling interval of unit time (example 1 [s], etc.).

  As an example of the smoothing characteristic, for example, there is a characteristic in which the fluctuation range of the combined output of the wind power generation system is 10% or less of the predetermined output of wind power generation for 20 minutes starting from an arbitrary time section. As an example of the smoothing algorithm, there is a low-pass filter operation using a moving average or a product-sum operation in addition to the first-order lag operation. However, by appropriately determining the time constant, almost all filters are used in the application of this embodiment. It can be used as well. In addition to the above, the fluctuation mitigation method includes a method of keeping the combined output of the wind power generation system at a constant value for a predetermined time. Each time a new smoothing standard or method is set for the purpose of contributing to the stabilization of the power system, the smoothing method is added to the maintenance charge success rate calculation unit 114 to be described later. The series of processes of the present invention can be similarly applied.

  The storage battery bank 101 relieves fluctuations in the electric power from the wind power generator 110 by connecting and discharging to the external system 108 by performing charging / discharging that is substantially opposite in phase to the power generation accompanying fluctuations generated by the wind power generator 110. To go. In the present invention, two or more storage battery banks 101 are assumed to be used for fluctuation mitigation operation. Each storage battery bank is composed of one or more storage batteries. As an example, when the voltage is approximately the same as the output voltage of the wind power generator, there are approximately 200 to 300 series connections. Each storage battery bank can be independently charged and discharged by an independent converter 102.

  The storage battery system including the storage battery bank 101 includes a leveling control unit 103, a maintenance charge success rate calculation unit 114, and a wind condition / power generation amount / charge / discharge amount data holding unit 115. If the maintenance charge success rate data is not updated after being stored in the maintenance charge success rate data holding unit 113, the maintenance charge success rate calculating unit 114 and the wind condition / power generation amount / charge / discharge amount data holding unit 115 are designed. It is used only for the time and does not necessarily have to be connected to the leveling control unit 103.

  The leveling control unit 103 includes an SOC calculation unit 104 (charge state calculation unit) that calculates a state of charge (SOC), a charge / discharge control unit 105, a maintenance charge request activation unit 106, a maintenance charge start determination unit 107, A maintenance charge necessary bank information holding unit 111, a storage battery specification holding unit 112, a maintenance charge success rate data holding unit 113, and a maintenance charge postponement time holding unit 116 are included.

  The leveling control unit 103 has a function of setting a fluctuation range of electric power supplied to the external system 108 within a predetermined range in response to fluctuations in wind conditions at a certain time. For example, the control is such that the fluctuation range of the electric power output from the wind power plant to the external system 108 is within 10% of the rated output of the wind power plant with respect to 20 minutes of wind accompanied by a change in wind speed.

  The SOC calculation unit 104 calculates the SOC from various measurement data such as the current, voltage, temperature, integrated current value, open circuit voltage (OCV) of the storage battery bank 101.

  The maintenance charge request activation unit 106 activates a start request for equal charge in the operation of the lead storage battery or an OCV acquisition operation (maintenance charge including both) of the lithium ion storage battery. As the start of the maintenance charge request, periodically (for example, every two weeks), when the variation between the cells of the lead storage battery exceeds a predetermined value, or the SOC calculated from the current integrated value and the SOC calculated from another index When the deviation exceeds a predetermined value, there are activation by an operator's manual operation, remote activation from a host system or the like that integrally controls more systems.

  The maintenance charge request activation unit 106 receives a signal from the external input 117 (a transmission source is software such as SCADA in a console or a device installed near / remotely). The maintenance charging start determination unit 107 can send a signal to an operation console (or software such as SCADA in a nearby / remote device) via an external output 118. In addition, 117 and 118 are not limited to input devices and output devices on the console, but are general-purpose input / output including remote communication, and are responsible for general signal transmission / reception in the leveling control unit 103. To do.

  The maintenance charging necessary bank information holding unit 111 holds information such as how many storage battery banks 101 need maintenance charging at a certain point in time. An example of the information to be held is information such that the variation exceeds a predetermined value in two banks out of the six-bank configuration and maintenance charging is necessary. The storage battery specification holding unit 112 holds various specifications related to the fluctuation mitigation operation, such as the capacity of each storage battery bank 101 and the maximum charge / discharge current value.

  The maintenance charge success rate data holding unit 113 performs maintenance charge on one or more storage battery banks that are smaller than the total number of the storage battery banks. Then, the maintenance charge success rate data holding unit 113 can complete the maintenance charge without exceeding the operation conditions of the remaining bank when the fluctuation mitigation operation is continued only in the storage battery bank (residual bank) that does not perform the maintenance charge. The probability is obtained for each SOC value at which maintenance charging is started. Here, the SOC value at which maintenance charging is started means the SOC value during fluctuation mitigation operation immediately before starting maintenance charging.

  In the case where the capacity obtained by adding up the storage battery capacities of all banks is a capacity that is not excessive or insufficient for fluctuation mitigation operation in which charging / discharging is performed in the storage battery so that the smoothed value of the wind power generator output becomes the combined output as described above, the storage battery In the ideal state, the bank does not fail such as exceeding the SOC range, and the relative relationship between the internal state quantities can be uniquely determined.

  In the calculation example of the present invention, the calculation example under the ideal condition is shown. On the other hand, the present invention is similarly applied by obtaining a maintenance charge success rate parametrically for each added control coefficient even when control such as allowing a certain failure rate and causing the SOC to follow a certain value is included. it can. Here, the failure rate is the fluctuation mitigation operation in the remaining storage battery banks that do not perform maintenance charging when maintenance charging is performed on some of the plurality of storage battery banks while continuing the fluctuation mitigation operation. The probability of bankruptcy. The maintenance charge success rate used in the maintenance charge success rate data holding unit 113 is the start of operation of the wind condition data observed prior to the construction of the installation site of the wind power generator or the power generation amount data of the adjacent wind power plant It is created based on previously acquired data or data acquired while performing fluctuation mitigation operation after the start of operation of the wind power plant.

  The maintenance charge success rate data may include a plurality of maintenance charge success rate curves for each condition according to the conditions at the time of creation of the data. The wind conditions around Japan are known to vary greatly from season to season, and it is generally known that the winter is more affected by seasonal winds and the wind tends to be larger.

  For example, when the power generation amount of the wind power generator used for the analysis is winter data, it is used to calculate a winter maintenance charge success rate curve. When actually performing maintenance charging after the start of the operation of the wind power plant, the maintenance charging success rate curve held for each season is an RTC (real time clock, calendar, time) (not shown) held by the external input 117 or the leveling control unit 103. Etc.) is switched according to the information on the season acquired from the Selection of multiple maintenance charge success rate curves according to the conditions at the time of creating the maintenance charge success rate data above is the maintenance charge success rate curve when the maintenance charge success rate is created and when actual maintenance charge is performed after the start of operation. If a method in which the conditions at the time of selection are (approximately) matched, it is possible to extend other conditions other than the season.

  For example, wind speed trends (such as ocean and land winds) that change with time, wind speed trends due to weather, wind speed trends due to wind direction (neighboring topography, mutual influence with adjacent wind generators, etc.), weather data or weather forecasts Maintenance charge success rate curve that corresponds to the condition of wind speed, such as the wind speed trend depending on the data value, and that corresponds to the maintenance charge success rate curve when calculating the maintenance charge success rate curve and after the start of operation. Any kind of data can be used as long as it can be input from an external input 117 or an information source inside the leveling control unit 103.

  The wind condition / power generation / charge / discharge amount data holding unit 115 holds various data for calculating the maintenance charge success rate. In both cases, long-term data such as annual and monthly data is desirable. Further, data measured after the start of operation of the site may be used, and maintenance charge success rate data may be continuously updated using both the data before the start of operation and the data after the start of operation.

  The maintenance charge success rate calculation unit 114 uses the data held in the wind condition / power generation amount / charge / discharge amount data 115 and assumes that maintenance charge has started for some banks, and performs maintenance charge until the maintenance charge is completed. The probability that the fluctuation mitigation operation can be continued without exceeding the capacity of the remaining bank with only the remaining bank that is not performed is obtained for each SOC at the start of maintenance charging. According to the above calculation, maintenance charge is performed for 2 banks while continuing fluctuation mitigation operation in 3 banks out of all 5 banks of storage batteries, for example, by performing for multiple cases with various conditions such as bank configuration. When performing, it is possible to know in advance the probability that maintenance charging can be completed.

  Since the maintenance charging success rate greatly varies depending on the SOC value at which maintenance charging is started, the operation rate of the wind power site can be improved by starting maintenance charging from an SOC with a higher success rate. When the maintenance charge request determination unit 107 receives a maintenance charge request from the maintenance charge request activation unit 106, the maintenance charge start determination unit 107 receives the SOC value of the storage battery from the SOC calculation unit 104 and the maintenance charge from the maintenance charge necessary bank information holding unit 111. Information on the number of necessary banks, storage battery banks that require maintenance charging, and storage battery specifications such as maximum charge / discharge current values and capacities of storage battery banks that continue fluctuation mitigation operations (from storage battery specification holding unit 112 Based on the information, the start of maintenance charging is determined.

  When the charge / discharge control unit 105 receives a maintenance charge start command, for example, the charge / discharge control unit 105 performs maintenance charge on the other storage battery bank in a predetermined procedure while continuing the fluctuation mitigation operation in one storage battery bank.

  When the maintenance charge start determination unit 107 receives the maintenance charge request from the maintenance charge request activation unit 106, the maintenance charge success rate based on information such as the current SOC value and the number of storage battery banks required for maintenance charge is a predetermined value. If lower, the maintenance charge start command is not output immediately after receiving the maintenance charge request, and the maintenance charge start command is temporarily suspended until the maintenance charge success rate shifts to a higher state. For example, when there are two storage battery banks and the SOC is around 50%, the success rate when maintenance charge is started for one of the storage batteries is almost 0%, but the maintenance charge success rate after 10 or more hours Improves to over 35%. This is as shown in FIG.

  The start of maintenance charging can be suspended because, in many cases, the grace time until maintenance charging starts is relatively long. For example, conventionally, maintenance charging (equal charging) of a lead storage battery may be performed at a constant interval of two weeks, but the effect when the interval of two weeks is extended by more than ten hours is considered to be slight.

  However, on the other hand, there are cases where the error in the SOC indication value of the lithium ion battery is clearly large, and if the maintenance charge (accurate OCV acquisition due to suspension) is not performed immediately, the operation will be hindered. Can also exist. Therefore, the maintenance charge grace time holding unit 116 holds the maximum grace time during which the maintenance charge start determination unit 107 can hold the start of maintenance charge, and the maintenance charge success rate depends on the current maintenance charge success rate. First, the maintenance charging start determination unit 107 may output a maintenance charging start command. Alternatively, a message may be displayed on the console via the external output 118 to ask for instructions from the operator. Note that the grace time stored in the maintenance charge grace time holding unit 116 is not necessarily fixed, and can be varied depending on the degree of urgency of maintenance charge (for example, the degree of variation between cells, the degree of increase in SOC error, etc.). Also good.

  The arrangement, configuration, and the like of the leveling control unit 103, the maintenance charge success rate calculation unit 114, and the wind condition / power generation amount / charge / discharge amount data holding unit 115 are not limited to the above-described examples. Any configuration may be used as long as it exhibits the above. The maintenance charge success rate calculation unit 114 may be included in the leveling control unit 103, and the maintenance charge success rate may be calculated by the leveling control unit 103.

(Description of FIG. 2)
FIG. 2 shows an example of a maintenance charge success rate curve with respect to the SOC at the start of maintenance charge. The horizontal axis is the SOC at the start of maintenance charging, and the vertical axis is the maintenance charging success rate. Note that the storage battery capacity is the minimum necessary configuration, and it is assumed that the SOCs of all banks are linked and relaxed. The maintenance charge success rate on the vertical axis is the probability that maintenance charge can be completed without exceeding the capacity of the storage battery bank that continues the fluctuation mitigation operation when maintenance charge is performed on some storage battery banks.

  In this figure, a curve 130 shows another storage battery bank while continuing the fluctuation relaxation operation by one storage battery bank in a fluctuation relaxation system having two storage battery banks having the same current capacity and the same Ah capacity. Shows the success rate when performing maintenance charging. Similarly, the curve 131 shows a case where six storage battery banks having the same current capacity and the same Ah capacity are provided, and maintenance charging is performed on one storage battery bank while continuing the fluctuation mitigation operation with the five storage battery banks. It shows the success rate. Furthermore, the curve 132 is a fluctuation mitigation system (two capacity battery ratios, both of which are the current capacity ratio and the Ah capacity ratio 2: 1) (the capacity ratio is expressed as a rectangular area representing the bank in the figure). The success rate in the case where maintenance charging is performed on one storage battery bank having a larger capacity while continuing the fluctuation mitigation operation by one storage battery bank having a smaller capacity.

  The maintenance charging time was 10 hours. In addition, the curve 130 indicates, for example, six storage battery banks having the same capacity for three storage battery banks, in addition to a case where maintenance charging is performed for one storage battery bank of two storage battery banks having the same capacity. It can also be applied to maintenance charging at the same time. Similarly, the curve 132 can be applied to the case where, for example, three storage battery banks having the same capacity are simultaneously subjected to maintenance charging for two storage battery banks.

  Hereinafter, the present invention can be similarly applied to other cases where the ratios of current capacity and charge / discharge capacity are the same or similar. By expanding the capacity ratio to a non-integer ratio instead of the bank composition unit and finding the curve in this figure parametrically, it becomes possible to deal with more general cases, and the same procedure for a wide variety of storage battery combinations Can be applied.

  As can be seen from the curve in this figure, success in performing maintenance charging for some banks during fluctuation mitigation operation according to the SOC value for starting maintenance charging and the ratio of banks performing maintenance charging in all banks The rate varies greatly. Therefore, by effectively utilizing this characteristic, it is possible to start maintenance charging under a more advantageous condition with a high maintenance charging success rate, and the operating rate of the power plant can be improved.

  Here, as an example, when the storage battery for fluctuation mitigation has two storage battery banks having the same capacity, when the SOC is 55%, a maintenance charge request is sent from the maintenance charge request activation unit 106 to the maintenance charge start determination unit 107. I think it was made.

  The maintenance charging curve in the case of two storage battery banks having the same capacity corresponds to the curve 130 in FIG. As can be seen from this figure, the maintenance charge success rate corresponding to SOC 55% on the horizontal axis of the curve 130 is almost 0%. Accordingly, the maintenance charge start determination unit 107 reserves the output of the maintenance charge start command to the charge / discharge control unit 105 in cases other than an imminent situation where maintenance charge is immediately required.

  Thereafter, with the passage of time, the maintenance charge start determination unit 107 outputs a maintenance charge start command to the charge / discharge control unit 105 in anticipation of the transition to the SOC corresponding to a higher maintenance charge success rate.

  Next, a procedure for creating a maintenance charge success rate curve will be described.

  FIG. 3 is a flowchart showing an example of a process for creating a maintenance charge success rate curve.

  The maintenance charge success rate curve is created by the maintenance charge success rate calculation unit 114 shown in FIG. First, measurement data serving as a basis for calculating the maintenance charge success rate is obtained from the wind condition / power generation / charge / discharge amount data holding unit 115 (S501). For example, in the case of wind power generation, the wind condition of the planned construction site may be measured over a considerable period (such as one year or more) prior to construction. If there is a wind power plant already in operation in the vicinity, obtain as much power generation data as possible. In the latter case, it is more preferable if it is time-series data of the power generation amount of the same type of wind power generator.

  If the obtained measurement data is, for example, wind speed data, it is converted into power generation time-series data by a known method such as a third law of the wind speed of the power generation. In this example, an example of creating a maintenance charge success rate curve based on prior data before the start of operation of the wind power plant was shown, but a maintenance charge success rate curve is similarly created based on actual measurement data after the start of operation. It is possible to add and / or update the data in advance. When using data after the start of operation, there is an advantage that no error due to various assumptions occurs compared to the case of pre-simulation. On the other hand, since the amount of accumulated data is small immediately after the start of operation, statistical bias is avoided by adding prior data before the start of operation or statistical wind condition data using a Weibull coefficient.

  Next, in S502, the behavior when the storage battery is charged / discharged by a general known fluctuation mitigation algorithm, such as setting a smooth value due to the first-order delay of the power generation amount as an output follow-up target, is analyzed. As examples of fluctuation relaxation, those shown in the above mathematical formulas (1) to (3) can be used. The analysis method will be described in detail with reference to FIG. A maintenance charge success rate map is created based on the analysis result.

  The obtained analysis result data is stored in the maintenance charge success rate data holding unit 113 of the leveling control unit 103 in FIG. 1 (S503).

  Thereafter, a maintenance charge start determination task is started using the above data (S504). This will be described later with reference to FIG.

  Hereinafter, the analysis method will be described with reference to FIG.

  FIG. 4 is a graph illustrating an example of a process for determining success in maintenance charging.

  In the figure, the upper right graph shows the change over time of the current generated by the wind power generator. Here, the value shown as the current is the value of the current when the electric power generated by the wind power generator is adjusted to a predetermined voltage and normalized as necessary.

  The lower right graph shows a change with time in the state of charge (SOC) of one of a plurality of storage battery banks constituting the fluctuation mitigation system. The maintenance charging time is 10 hours.

  The graph on the left side of the figure shows the probability of successful maintenance charging in a certain state of charge (SOC). This is the same as FIG.

  The analysis is performed on the assumption that maintenance charging has been started from all start times with respect to whether or not both the current limit value and the SOC range of the storage battery bank that does not perform maintenance charging that continues the fluctuation mitigation operation are exceeded. Here, for the sake of simplification, it is assumed that the maintenance charging uses another power source other than the wind power generator subject to fluctuation mitigation.

  The graphs in the upper right and lower right of FIG. 4 show, as an example, in a fluctuation mitigation system having two storage battery banks having the same current capacity and the same Ah capacity shown by the curve 130 in FIG. This is a case where maintenance charging is performed on another storage battery bank while continuing the fluctuation mitigation operation. In the graph of FIG. 4, it is assumed that maintenance charging is started from time t1, and that the fluctuation mitigation operation is continued in the other bank. In this case, since the capacity of the storage battery constituting the fluctuation mitigation system is halved, the limit value of the charge / discharge current is halved from Idmax to Idmax / 2 (discharge) and Icmax to Icmax / 2 (charge) in the figure. .

  Under this condition, if the above limit value is not exceeded for 10 hours during which maintenance charging is continued, it is determined that there is no excess regarding the current limit value (symbol 143).

  Similarly, the SOC of the storage battery bank that continues the fluctuation mitigation operation changes with a slope twice that of the conventional one as shown by the dotted line in the lower right graph when the other bank is performing maintenance charging. Even in this case, if the SOC changes within the limit range during the duration of the maintenance charge, it is determined that there is no excess regarding the SOC (reference numeral 142).

  In this case, since it is determined from reference numerals 143 and 142 that neither the current nor the SOC is exceeded, the cumulative frequency of “successful” maintenance charge success rates for the SOC1 corresponding to the maintenance charge start time t1. 1 is added to.

  It should be noted that the frequency is accumulated for the class range having a certain width including SOC1 because of the aggregation as a histogram. An example of the width of the class range is 5% of the SOC. However, when there is a lot of data to be statistically processed, even if a narrower width is adopted, the statistically significant frequency can be tabulated. Conversely, when there is little data to be processed, the class range is widened and the accumulated frequency is secured to an amount that can be regarded as statistically significant. An example of a criterion for determining whether the frequency is significant is whether the histogram changes smoothly. When the class range is narrowed despite the fact that there is little data to be processed, the variation in the frequency of adjacent classes becomes large. Alternatively, the success / failure count for the SOC1 may be retained as it is without being subjected to the histogram processing, thereby confirming a change in the histogram with respect to the width of different class ranges. Similarly, the success / failure count for the SOC 1 that is not subjected to histogram processing may be stored for the purpose of histogram processing together with the success / failure count obtained in the additional statistical processing later.

  Similarly, when maintenance charging is started from time t2, since the SOC is lower than the lower limit (reference numeral 146), 1 is added to the cumulative frequency of “failure” of the maintenance charging success rate for the corresponding SOC2.

  Further, when maintenance charging is started from t3, because the maximum discharge current value is exceeded (reference numeral 149), 1 is added to the cumulative frequency of “failure” of the maintenance charging success rate for the corresponding SOC3.

  As in the case where maintenance charging is started from time t2, regarding the excess of the SOC, even if the current limit value is not exceeded, the SOC may be exceeded.

  For example, when fluctuation mitigation operation is performed in two banks without performing maintenance charging, maintenance charging for one bank is performed at the timing corresponding to the situation where the SOC increases from 50% to 80% (30% increase). In this case, the other bank that continues the fluctuation mitigation operation changes from 50% to 110% (up 60%), clearly exceeding the SOC limit range. When starting from an intermediate SOC in the SOC operation range, the SOC of the storage battery bank on the side where the fluctuation mitigation operation is continued tends to occur from the viewpoint of the change width of the SOC.

  In addition, if a general well-known fluctuation mitigation algorithm such as a smoothing value due to the first-order lag of the generator output is used as the output follow-up target due to the basic nature of the wind intensity distribution, stagnation at an intermediate SOC The time is relatively short, and there is also a property of shifting to one of the SOCs (especially, the lower SOC) without waiting for a long time. Therefore, when performing maintenance charging for the fluctuation mitigation operation, it is very disadvantageous to start from an intermediate SOC.

  The above procedure shows the calculation of the maintenance charge success rate performed in S502 of FIG. 3. In this case, various bank configurations, current limit values for each bank, capacity, maintenance charge time (for example, OCV state) The time required to set the time, the push-in charge time for equal charge, etc., with optional settings), the type of storage battery, changes in the wind conditions for each season, differences in characteristics for each generator, and power generation that pauses among multiple generators When there is enough data to perform statistical processing, such as when there is a machine, calculating the maintenance charge success rate under various conditions will yield a maintenance charge success rate that matches the state during operation. Can be created.

  Next, the calculation result is stored in the maintenance charge success rate data holding unit 113 in S503 of FIG. This storage operation may be performed only once before starting the operation of the wind power plant when it is based on the wind condition data before construction of the wind power plant. Based on the actual data after the start of operation, measurement data relating to the wind generator actually used may be used and updated as needed. Therefore, the wind condition / power generation amount / charge / discharge amount data holding unit 115 and the maintenance charge success rate calculation unit 114 may be used only before the operation is started or may be continuously used after the operation is started. After the maintenance charge success rate data is stored, application of maintenance charge during the fluctuation mitigation operation based on the maintenance charge success rate data is actually started. Of course, the maintenance charge during the fluctuation mitigation operation may not be applied at the start of power plant operation, but may be applied after sufficient performance data has been accumulated.

  As an example of wind condition data, there is a Weibull distribution representing an appearance rate distribution of wind speed. The Weibull distribution is generally represented by the following formula (4).

  In the equation, f (V) is the appearance rate of the wind speed V, c is a scale factor, and k is a shape factor.

  Next, a task flow regarding determination of the start of maintenance charging will be described. These flows operate in association with a plurality of functional blocks in the leveling control unit 103 of FIG.

  FIG. 5 is a flowchart showing an example of the maintenance charge start determination task.

  First, in S510, the maintenance charge request activation unit 106 generates a maintenance charge start request trigger. Factors for trigger occurrence include, for example, when the period for regular maintenance charging comes every two weeks, etc., or when voltage variation (SOC variation) among a plurality of storage batteries in the bank exceeds a predetermined value. There is a maintenance charge command input by manual operation, and a remote maintenance charge command from a host system that is centrally managed including other power generation sites.

  Operator operations and remote commands are input from the external input 117. In addition, the trigger of a fixed period such as two weeks may be input from the external input 117 or may be triggered from a real time clock (not shown) inside the leveling control unit 103. The cell-to-cell variation is calculated from the measurement data input to the leveling control unit 103.

  However, when the maintenance charge start request trigger is generated in S510, the maintenance charge start request is only a request for maintenance charge, and the maintenance charge start determination unit 107 considers other factors in determining whether to actually start maintenance charge. Judgment. One of the steps is S511.

  Here, the maintenance charge success rate at that time is calculated by referring to the corresponding maintenance charge success rate data from various conditions such as the current SOC value, bank configuration, the number of banks required for maintenance charge and the desired maintenance charge time. To do. When referring to the maintenance charge success rate data, the state such as season and weather is input from the external input 117, and for example, by referring to the corresponding maintenance charge success rate data for each season and every weather, the accuracy is higher. Maintenance charge success rate data can be obtained.

  In fact, in the vicinity of Japan, it is known that the influence of seasonal winds is noticeable due to the climate that changes from season to season, and there are many places where the wind conditions differ greatly between winter and summer. Similarly, since the wind conditions differ depending on the general tendency of the weather, the characteristics of the maintenance charging success rate also change. Therefore, the accuracy of the maintenance charge success rate can be improved by switching the data of the maintenance charge success rate to be applied to the corresponding weather according to the weather.

  In general, it is difficult to predict the wind speed itself up to several hours later using weather forecast data and use it for fluctuation mitigation operation because of current prediction accuracy. On the other hand, as in the present embodiment, when the current weather data is used to switch the data group statistically processed for the relationship with the weather, an effect can be expected by averaging.

  For example, in the case of cloudy weather, it is expected that the influence of solar radiation is small and the fluctuation of wind power is small compared to clear weather. In the case of wind generators facing the mountains and the sea, for example, if the wind direction is used as an example of weather data, it is expected that there will be little fluctuation for the wind from the sea, and conversely for the wind from the mountains It is expected that the turbulence caused by the topography will cause large fluctuations in wind conditions. In addition, the maintenance charging success rate may be switched according to the time zone. This utilizes the tendency that the wind speed is low in the early morning and evening due to the effect of sea and land breeze.

  Based on the calculation result, it is determined in S512 whether the success rate is equal to or higher than a threshold value. If the success rate is equal to or greater than the threshold value, it is determined that maintenance charging during fluctuation mitigation operation is possible with a sufficiently high probability, and the maintenance charging start determination unit 107 instructs the charging / discharging control unit 105 to start maintenance charging in S518. To do. The charge / discharge control unit 105 sends a command value to the converter 102 so as to perform maintenance charging on the storage battery bank 101 to be subjected to maintenance charging in the fluctuation mitigation system in accordance with the designated maintenance charging method. Regarding the method of maintenance charging, in lead-acid batteries, there are equal charging for preventing variation between cells, or charging for resetting the integrated current value.

  In the lithium ion storage battery, charging / discharging for obtaining an open circuit voltage (OCV), charging for avoiding a closed circuit voltage gradient flat portion (CCV voltage gradient flat portion) with respect to the SOC, or the like can be given. To avoid the voltage gradient flat part, for example, by shifting the SOC to a high or low part, the closed circuit voltage (CCV) changes greatly with respect to the SOC change, and the deviation of the SOC is corrected (reset of the SOC gauge). belongs to. The OCV may be acquired not only for the lithium ion storage battery but also for other storage batteries including a lead storage battery. In the present embodiment, it is assumed that a separate power source (not shown in FIG. 1) is used as the power source for uniform charging accompanying SOC charging and SOC adjustment.

  In addition, the maintenance charge success rate calculation unit 114 calculates the maintenance charge success rate by using the bus 109 of the fluctuation mitigation system as a power source without using a separate power source, and the maintenance charge success rate data holding unit By holding at 113, maintenance charging without using a separate power source can be handled. The maintenance charging success rate of both the method using a separate power source and the method not using it for maintenance charging may be held in the maintenance charging success rate data holding unit 113 and switched according to the maintenance charging method actually performed.

  In the maintenance charging method using the bus 109 as a power source, the power for maintenance charging may be supplied (absorbed) from the wind power generator 110. Further, the power for maintenance charging may be supplied from another storage battery bank 101 that is not subject to maintenance charging. Furthermore, only other storage battery banks may absorb power from the power source. Furthermore, the power for maintenance charging may be supplied (absorbed) from another power source (not shown) via the bus 109.

  S513 to S515 are optional and need not be applied, but convenience is improved.

  In S513, if the success rate of maintenance charging is less than the threshold value in S512 of the previous step, the maintenance charging success rate reaches a predetermined threshold based on the current value of SOC, the bank configuration, the number of banks required for maintenance charging, and other measured values and information. Calculate the expected waiting time until it exceeds. A method for calculating the waiting time will be described later.

  In S514, a threshold determination of the expected waiting time is performed.

  If the expected waiting time is greater than or equal to the threshold, the process proceeds to S515. When performing maintenance charging while continuing the fluctuation mitigation operation, a message indicating that there is a possibility that maintenance charging with a high success rate may not be performed within the desired waiting time is displayed or transmitted remotely, and regarding the selection of subsequent operations In addition to requesting the operator's instruction, the process proceeds to execution of exception handling 1.

  As an example of selection of the above-mentioned transition operation, maintenance charging is forcibly started or the operating rate is emphasized, and although it is stochastically low, it waits until the SOC situation improves, and then the fluctuation is reduced. There are selections such as whether to continue operation or pause and perform maintenance charging.

  As an example of the above exception processing 1, without waiting for the input of the operator's selection result, or when the input of the selection result has timed out, execution of maintenance charging is executed immediately or after waiting for the maximum waiting time At that time, the selection of whether or not to suspend the fluctuation mitigation operation is automatically executed according to a predetermined procedure. At this time, a more complicated procedure that is not presented when waiting for an operator's input instruction may be incorporated.

  For example, when 3 banks out of all 6 banks of storage batteries require maintenance charging, the waiting time until maintenance charging of 1 bank out of the banks requiring maintenance charging can be increased, and the waiting time of the other 2 banks is shortened. In the case of maintenance charging up to two banks, when the maintenance charging success rate is equal to or higher than the threshold, maintenance charging is applied only to the two banks.

  The threshold for the expected waiting time varies depending on the situation. For example, when starting regular maintenance charging every two weeks, the threshold can be set to several days on the assumption that the effect of extending the maintenance charging interval to several days is small. On the other hand, a short-term threshold value is set when the difference between the SOC value based on the current integration and the SOC value indication by another index is increased and the control is hindered. Of course, the threshold value is 0 in the case of an immediate execution command for starting maintenance charging by an operator input.

  S516 is a determination that the maximum waiting time has been exceeded when maintenance charging is suspended because the maintenance charging success rate is equal to or less than the threshold value. Similarly, in S516, it may be determined whether there is an urgent need to exceed the absolute compliance requirement other than the waiting time. For example, it is not a threshold value for generating a maintenance charge start request in S510, such as a variation, but a threshold value that must be strictly observed, which is more stringent (described as an absolute compliance requirement in S516. In step S516, the updated measurement is performed so as not to exceed the condition in which the value of A / D increases rapidly, such as the absolute maximum rating value of the electrical / electronic component, etc. while the start of maintenance charging is suspended. Judgment based on value and other information.

  If the maximum waiting time has been exceeded or if the absolute maximum requirement has been exceeded, exception processing 2 is performed in S517. This is similar to exception processing 1, except for the operation of waiting for the situation to improve until the maximum waiting time ends. Although not shown, when maintenance charging is immediately executed, it may be presented to the operator to select whether or not to continue the fluctuation mitigation operation in the storage battery bank that does not perform maintenance charging. If the maximum waiting time has not been exceeded, the process returns to S511 again, and the subsequent flow is executed again based on information such as the SOC current value that is continuously updated.

  Of course, the process of the immediate execution command for starting the maintenance charge by the operator's input does not execute the flow of FIG. 5, and the maintenance charge start determination unit 107 instructs the charge / discharge control unit 105 to perform the immediate maintenance charge start command. You may do it.

  FIG. 6 shows an example of the time transition of the maintenance charging success rate. The horizontal axis represents the waiting time until the start of maintenance charging, and the vertical axis represents the maintenance charging success rate.

  This figure explains that in the case of an SOC with a low maintenance charging success rate, the start of maintenance charging may be delayed. In other words, the maintenance charge success rate is improved by reserving the start of the maintenance charge.

  Specifically, in this figure, when the SOC is in the range of 55% to 60%, the maintenance charge is not performed immediately, and the maintenance charge is started after waiting for the time indicated on the horizontal axis. It shows the transition of maintenance charge success rate. As the bank configuration of the storage battery, data is shown in a case where maintenance charging is performed for one bank out of all two banks having the same capacity, and the fluctuation mitigation operation is continued in the remaining one bank.

  As can be seen from this figure, while the waiting time is 0 or very short, the maintenance charging success rate is low, but thereafter, the maintenance charging success rate increases in proportion to the passage of time. The maintenance charge success rate reaches almost saturation at a waiting time of about 13 hours. Thus, for example, when maintenance charging is started every two weeks, if the SOC at that time is around 55%, the success rate when performing maintenance charging while performing fluctuation mitigation operation by waiting about half a day It turns out that it shifts to high conditions.

  In this figure, the maximum value of the maintenance charge success rate on the vertical axis is not so large as 40% because the SOC when the maintenance charge start request is received is in the range of 55% to 60%. This is because the case is used as a sample, and the high success rate and the low success rate are averaged. For example, some samples have reached a higher maintenance charge success rate during the waiting time of about half a day, but after reaching a high maintenance charge success rate in a shorter time, the sample moves to a smaller maintenance charge success rate. Samples that are included.

  Accordingly, when the maintenance charge success rate threshold is reached for each sample, if the suspension is immediately stopped and the maintenance charge is started, the waiting time may be shorter. Using FIG. 6, the average waiting time until a predetermined maintenance charge success rate is reached can be calculated based on the SOC at the time when the maintenance charge start request is received. Now, when the maintenance charge success rate at which maintenance charging can be started is set to the threshold 170, the time corresponding to the threshold 170 can be determined as an average waiting time 171. As a method of determining a threshold value at which maintenance charging can be started, a method for determining the target operating rate of the wind power generation site is taken into consideration, and until the maintenance charging success rate shifts to a saturated state or a vibration state as shown in FIG. Determine from time etc. Of course, the threshold value is not necessarily fixed. For example, when the SOC becomes easy to move due to wind conditions that change from season to season, the possibility of shifting to an SOC with a high maintenance charge success rate increases in a short time. Thus, the threshold value of the maintenance charge success rate can be set to a high value.

In the present invention, the start of maintenance charging is suspended until a condition for a higher maintenance charging success rate is satisfied. Accordingly, there is a waiting time from when the maintenance charging start request is generated until the maintenance charging is actually started. _Assuming that the average value of the waiting time is t _avw , the maintenance charging interval is extended by t _avw as compared with a conventional method in which maintenance charging is performed at a constant cycle such as two weeks. Although there are many cases where there is no problem even if the maintenance charging interval is extended, if the maintenance charging interval is specified in the recommended operating conditions or the like, it is necessary to approach the target maintenance charging interval. _If a correction is made such that a time offset in advance by t _avw / 2 is set as the maintenance charge request interval for _m , the deviation from the conventional operation can be reduced. FIG. 7 shows an example of offsetting by half (t _avw / 2) of the average waiting time for maintenance charging in a fixed cycle. As a result of the offset, the timing at which the maintenance charge request activation unit 106 outputs the maintenance charge start request to the maintenance charge start determination unit 107 shifts from the point A surrounded by the inverted triangle in FIG.

  In this figure, the shaded portion 180 represents a maintenance charge location relating to a certain storage battery bank, and the white masking unit 181 represents an operation location of fluctuation mitigation operation relating to the same storage battery bank.

  In this figure, reference numeral 182 denotes the previous maintenance charge and subsequent fluctuation mitigation operation, and similarly, the middle to lower reference numeral 183 denotes the next maintenance charge and the subsequent fluctuation mitigation action related to the same storage battery bank as 182. It corresponds to the location of operation.

In addition, when the probability of maintenance charging at time-out due to wind conditions, etc. is high, the generation density during t _avw period is biased. _Therefore , the offset is not limited to t _avw / 2, and the offset considering the appearance frequency of the waiting time It is also good.

The above example is for a case where a maintenance charge start request is made at a fixed time interval, but various errors due to the maintenance charge waiting time can be reduced similarly by applying an offset for another index instead of time. . For example, when a maintenance charge start request is generated according to the degree of variation between cells in the same storage battery bank, assuming that the tendency of increase in variation can be predicted in advance by extrapolation or the like, from the time when the variation reaches a threshold, t _avw / 2, or by using a value obtained by subtracting the variation corresponding to time such as t _avw or t _avw + 3σ as a threshold, the probability of exceeding the target variation threshold can be reduced.

In this method, in addition to t _avw / 2, a time corresponding to t _avw or t _avw + 3σ (generally t _avw + nσ, where n is _increased or _decreased depending on conditions) may be subtracted from the threshold value. This is to prevent the maximum variation from exceeding the range that must be observed even in the case of the maximum waiting time. The same-type threshold determination may be performed in S516 as described above.

  In the above embodiment, an example of wind power generation has been shown. However, the power generation amount fluctuates in solar power generation and other power generation, and it can be similarly applied to power generation means in which the fluctuation is difficult to foresee. The storage battery is not limited to a lead storage battery and a lithium ion secondary battery, and other types of storage batteries may be applied. Moreover, the same method can be applied to the case of temporary disconnection for the purpose of inspection other than the suspension for equal charge and OCV acquisition.

  According to the present invention, when maintenance charging is performed during the fluctuation mitigation operation with a configuration having no surplus battery capacity, the capacity of the other storage battery bank that continues the fluctuation mitigation operation (chargeable / dischargeable charge amount, maximum charge / discharge) The probability that maintenance charging can be completed without exceeding (current value) greatly varies depending on the SOC value at which maintenance charging starts and the bank configuration of the storage battery. For example, when maintenance charging is started from a certain SOC value in a certain bank configuration, the probability that maintenance charging can be completed without exceeding the capacity of the remaining banks that do not perform maintenance charging is almost zero. Therefore, if the above conditions are known in advance, maintenance charging can be started while avoiding such conditions, so that maintenance charging can be performed while continuing the fluctuation mitigation operation, and the operating rate of the power generation equipment can be improved.

  In all the embodiments described above, the power generation apparatus subject to fluctuation relaxation is not limited to a renewable one, and for all power supplies having statistical characteristics of output fluctuation capable of creating a maintenance charge success rate curve, The same applies.

  101: storage battery bank, 102: converter, 103: leveling control unit, 104: SOC calculation unit, 105: charge / discharge control unit, 106: maintenance charge request activation unit, 107: maintenance charge start determination unit, 108: external system, 109: Busbar, 110: Wind power generator, 111: Maintenance charge necessary bank information holding unit, 112: Storage battery specification holding unit, 113: Maintenance charge success rate data holding unit, 114: Maintenance charge success rate calculating unit, 115: Wind State / power generation amount / charge / discharge amount data holding unit 116: maintenance charge grace time holding unit 117: external input 118: external output 130, 131, 132: curve, 170: threshold, 171: average waiting time.

Claims (9)

A system that mitigates fluctuations in the amount of power transmitted from a generator,
It has a plurality of storage battery banks that can be charged and discharged independently, a leveling control unit, and a maintenance charge success rate calculation unit,
The storage battery bank includes a plurality of storage batteries,
The leveling control unit includes a charge state calculation unit and a charge / discharge control unit,
The leveling control unit or the maintenance charging success rate calculation unit performs maintenance charging on a part of the storage battery bank and continues the relaxation of the fluctuation by the remaining storage battery bank. It has a function to calculate in advance the relationship between the maintenance charge success rate, which is the probability that the maintenance charge can be completed without exceeding the operational limit, and the state of charge at the start of the maintenance charge, and to store data related to this relationship. And
The maintenance charge success rate is calculated from wind / power generation / charge / discharge data,
When the maintenance charge is required, the maintenance charge success rate is calculated by referring to the data related to the relationship, and the maintenance charge success rate is compared with a preset threshold value, and the result is equal to or less than the threshold value. In this case, a determination is made to reserve the start of the maintenance charging.   2. The data according to claim 1, wherein the data is created using a condition including a ratio between a capacity of the storage battery bank that performs the maintenance charging and a capacity of the storage battery bank that continues the fluctuation mitigation operation as a parameter. Storage battery system.   The leveling control unit calculates an average waiting time until the maintenance charging success rate is equal to or higher than a threshold using the state of charge at the start of the reservation when the reservation is made, and elapse of the average waiting time The storage battery system according to claim 1 or 2, wherein the maintenance charging is started later.   The leveling control unit compares the average waiting time with the maximum waiting time during which the maintenance charge can be reserved, and based on the result, presents a selection to an operator or starts the maintenance charge that is determined in advance. The storage battery system according to claim 3, wherein:   The storage battery system according to any one of claims 1 to 4, wherein the wind condition data included in the wind condition / power generation amount / charge / discharge amount data is approximated by a Weibull distribution. A plurality of storage battery banks that can be charged and discharged independently, a leveling control unit, and a maintenance charge success rate calculation unit, are used for a storage battery system that relaxes fluctuations in the amount of power transmitted from a generator,
When maintenance charge is performed on a part of the storage battery bank and the relaxation of the fluctuation is continued by the remaining storage battery bank, the probability that the maintenance charge can be completed without exceeding the operation limit of the remaining storage battery bank A computer-readable database characterized by a relationship between a certain maintenance charge success rate and a state of charge at the start of the maintenance charge.   7. The computer-readable database according to claim 6, wherein the maintenance charge success rate is calculated from wind condition / power generation / charge / discharge data.   8. The computer-readable database according to claim 7, wherein the wind condition data included in the wind condition / power generation / charge / discharge amount data is approximated by a Weibull distribution.   A computer-readable recording medium comprising the computer-readable database according to claim 6.

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