JP2018057092A - Power storage device control method, power storage device control apparatus, and power storage system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device control method, a power storage device control apparatus, and a power storage system which allow efficient operation of a power storage device even when an estimated value obtained by estimating a future load demand contains a great error.SOLUTION: A control method for a power storage device 20 which supplies power to a load 50, comprises: a step of calculating an estimated value of power to be consumed by a load 50 after the current time point on the basis of an actual value of power consumed by the load 50 during a predetermined time period till the current time point; and a step of determining a discharge amount of the power storage device for a next time point following the current time point on the basis of the estimated value, wherein the step for calculating an estimated value and the step for determining a discharge amount are repeatedly performed at a predetermined time interval.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for controlling a power storage device, a power storage device control device, and a power storage system.

  There are several purposes for installing power storage systems installed in electricity consumers, one of which is to reduce electricity charges. Specifically, by discharging the stored electricity during high demand, the contract power can be reduced by suppressing the maximum power, that is, the basic charge of the electricity charge can be reduced. The power storage system generally includes a power storage device that actually charges and discharges power and a power storage device control device (hereinafter simply referred to as “control device”) that controls the charge and discharge. When the controller determines the charge / discharge amount, it is necessary to conserve power in order to discharge at the time of high demand in the future. On the other hand, in order to suppress the maximum power, Appropriate control of charge and discharge is important, such as charging in a timely manner within a range where power is not renewed and preparing for subsequent discharge. Therefore, in the past, power demand (power used in the load) was monitored, and control was performed to discharge the amount of power demand exceeding the contract power, resulting in various controls to keep the received power within the contract power. An apparatus has been developed (see, for example, Patent Document 1).

JP-A-2006-116401

  If the contract power is given, the conventional control device can efficiently control the power storage device. However, in contracts where the contract power that has become popular in recent years is the actual amount system (maximum demand power in the past year is contract power), the demand curve of the day is predicted (demand forecast), and the demand curve and the current It is necessary to perform charging / discharging in a form in which received power is suppressed to the maximum by assigning charging / discharging based on the remaining battery level. However, it is difficult to accurately predict the demand of one consumer, and the predicted value includes a large error. Therefore, there is a problem that the above control is practically difficult.

  The present invention has been made in view of such a problem, and a method for controlling a power storage device capable of operating the power storage device efficiently even when the predicted value of the future demand for the load includes a large error. An object of the present invention is to provide a power storage device control device in which the control method of the power storage device is mounted, and a power storage system having the power storage device control device.

  In order to solve the above-mentioned problem, a control method for a power storage device according to the present invention is a control method for a power storage device that supplies power to a load. A step of calculating a predicted value of power used by a load after the current time based on the actual value, a step of determining a discharge amount of the power storage device at the current next time based on the predicted value, The step of calculating the predicted value and the step of determining the discharge amount are repeatedly executed at predetermined time intervals.

  Further, in the method for controlling the power storage device according to the present invention, the step of calculating the predicted value calculates the center value and the error width of the predicted value of the power used by the load after the current time based on the actual value. The corrected predicted value is calculated according to the center value and the error width of the predicted value, and the step of determining the discharge amount is based on the corrected predicted value and the power storage device at the current next time It is preferable to be configured to determine the amount of discharge.

Moreover, in the control method of the power storage device according to the present invention, the step of calculating the predicted value preferably calculates the predicted value corrected by the following equation.
Pe ′ (t) = Pe (t) + α × σ (t)
However,
Pe (t): Center value of predicted value σ (t): Standard deviation α: Coefficient α × σ (t): Error width t: Time

  Moreover, in the control method of the power storage device according to the present invention, the coefficient is preferably a negative value.

  Moreover, it is preferable that the control method of the power storage device according to the present invention changes the coefficient based on the remaining amount of the power storage device.

  Moreover, the power storage device control apparatus according to the present invention is characterized in that the above-described control method for the power storage device is mounted and controls the discharge operation of the power storage device.

  In addition, a power storage system according to the present invention includes a power storage device that supplies power to a load, and the above-described power storage device control device that controls a discharge operation of the power storage device.

  When the present invention is configured as described above, even when a predicted value that predicts the future demand of the load includes a large error, the method of controlling the power storage device that can efficiently operate the power storage device, It is possible to provide a power storage device control device in which a control method is implemented, and a power storage system including the power storage device control device.

It is a block diagram which shows the structure of an electric power storage system. It is a flowchart which shows the flow of charging / discharging amount determination processing. It is a graph for demonstrating the predicted value of the electric power used of load. It is a graph for demonstrating the relationship between the coefficient (alpha) and reduction achievement rate in a charging / discharging amount determination process. It is a graph which shows a result when an electric power storage apparatus is drive | operated by the charging / discharging amount determination process.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. First, the configuration of a power storage system having a power storage device control device (control device) in which the method for controlling a power storage device according to the present invention is implemented will be described with reference to FIG. The power storage system 10 includes a power storage device 20 configured by a secondary battery or the like, and a control device 30 that controls an operation state of the power storage device 20. In response to a command signal from the control device 30, the power storage device 20 receives power supply from the system 40 and stores (charges) power or supplies the stored power to the load 50 (discharges). It is configured as follows.

  The control device 30 includes a storage unit 32 that stores data for controlling the power storage device 20, and a processing unit 31 that determines the charge / discharge amount of the power storage device 20 based on the data stored in the storage unit 32. , And is configured. The processing unit 31 is configured by a computer CPU or the like, and the storage unit 32 is configured by a hard disk or the like. The main function executed by the processing unit 31 is to measure the power (current demand) used by the load 50, and use it during a predetermined time interval (for example, 30 minutes). From the process of storing power as history information in the storage unit 32 and the history information of power used by the load 50 stored in the storage unit 32 (as described above, for example, the value every 30 minutes), the power storage device And 20 processes for determining the charge / discharge amount.

  Then, the process (henceforth a "charge / discharge amount determination process") which determines the charge / discharge amount of the electric power storage apparatus 20 performed by the process part 31 of the control apparatus 30 is demonstrated using FIGS. In this case, the predetermined time interval is set to 30 minutes (that is, the power used is stored every 30 minutes, and the charge / discharge amount of the power storage device 20 is determined every 30 minutes). Will be described.

This charge / discharge amount determination process is a process executed by the processing unit 31 at the predetermined time interval (30 minutes) described above. As shown in FIG. 2, the processing unit 31 starts the charge / discharge amount determination process. Then, first, the history information (actual value, actual demand) of the electric power used from the current time (“t _n ”) to a predetermined period before (for example, “until three months ago”) is read from the storage unit 32 ( Step S100). And from this history information, the predicted demand of the load 40 from the current next time (“t _{n + 1} ”) to the predetermined time ahead, that is, the predicted value (predicted value) of the power used in this load 50 (Hereinafter, simply referred to as “predicted value”) is calculated (step S110). This predetermined time is, for example, 24 hours, and is hereinafter referred to as “N” (provided that N = 48 since 30 minutes), and Pe (t) is the predicted value (center value) at time t. (T _{n + 1} ), Pe (t _{n + 2} ),..., Pe (t _{n + N} ) are calculated. The calculation method of the predicted demand is performed by regression analysis using the history information described above, for example, but other methods may be used. When the predicted value Pe (t) is obtained in step S110, the standard deviation for each time when the central value Pe (t) is calculated (when this standard deviation is σ (t), σ (t _{n + 1} ), σ (t _{n + 2} ),..., Σ (t _{n + N} )) are calculated.

  FIG. 3 shows the predicted demand from 9:00 based on the actual demand up to 8:30 (history information of the power actually used at the load 50, which is indicated by a thick solid line in FIG. 3). It is the graph which calculated | required. A thin solid line indicates a predicted value (center value) Pe (t). In addition, the horizontal axis of FIG. 3 indicates time, and the vertical axis indicates power used (actual demand and predicted value). Note that FIG. 3 is a graph for 24 hours from 23 o'clock to 23:30 in order to display the actual value (actual demand) of the power used, but the actual predicted value Pe (t) and the standard deviation σ (t) is calculated for 24 hours from 9:00 to 8:30 on the next day.

Next, the processing unit 31 uses the predicted value Pe (t) and the standard deviation σ (t) to correct the predicted value of the used power of the load 50 at each time (time) based on the following formula (1). If the correction value at t is Pe ′ (t), then Pe ′ (t _{n + 1} ), Pe ′ (t _{n + 2} ),..., Pe ′ (t _{n + N} )) are calculated (step S120). In the following description, α × σ (t) in the equation (1) is referred to as an error width.

Pe ′ (t) = Pe (t) + α × σ (t) (t = t _{n + 1} , t _{n + 2} ,..., T _{n + N} ) (1)
However,
α: Coefficient

The processing unit 31 then calculates the demand P (t _n ) at the current time, the predicted value Pe ′ (t) for the predicted demand for 24 hours, the past maximum power (the past maximum power), and the current time based on the battery remaining amount of the power storage device 20, determines the charge and discharge amount D of the electric power storage device 20 of the current at the next time _{(t n + 1) (t} n + 1), the discharge amount D ( Based on t _{n + 1} ), a command signal is output to the power storage device 20 (step S130). In addition, although description of the determination method of charging / discharging amount is abbreviate | omitted here, a well-known method can be used. Further, the charge / discharge amount D (t _{n + 1} ) may be discriminated between the charge amount and the discharge amount based on the sign of the value.

  In general, when a predicted value is obtained by a mathematical method, in addition to the center value of the predicted value (the value that is most likely to occur and the predicted value Pe (t) described above), a confidence interval (a value with a predetermined probability) is used. Is a value that defines a range within the range), and the standard deviation σ (t) described above can be obtained. In determining the power charge / discharge pattern of the power storage device 20 using the predicted demand, it is common to use the center value (predicted value Pe (t)) with the highest certainty. This is optimal control if the actual demand matches the predicted value, and there is no problem.

  However, it is difficult to accurately determine the predicted demand of one consumer, and it is normal that actual demand deviates from the predicted value. Therefore, in the method using the central value (predicted value Pe (t)), when the actual demand deviates from the predicted value, the control is greatly different from the optimal control, and the effect of the power storage device 20 is sufficiently exhibited. It will not be possible.

  In the present embodiment, the predicted demand of the load 50 is not the central value (Pe (t)) of the predicted value, but as shown in the above-described equation (1), A correction value Pe ′ (t) is calculated on the basis of an error width α × σ (t) that is equal to or less than this value and lower than this value even if it is off), and this correction value Pe ′ (t) is used. As a result, it is possible to perform control without greatly impairing the optimality even when the prediction is lost. In the above equation (1), when the coefficient α is a positive value, the error width α × σ (t) is also a positive value. Therefore, the predicted demand is an upside value, and the coefficient α is a negative value. Since the error width α × σ (t) is also a negative value, the predicted demand is a downward value, and when the coefficient α is 0, the predicted demand is the center value of the predicted value. In FIG. 3, the upside value is indicated by a broken line, and the downside value is indicated by a one-dot chain line. When the upside is adopted as the predicted demand of the load 50, the remaining battery level of the power storage device 20 becomes empty on the way, and the risk of no control thereafter becomes small, but the risk of not fully utilizing the remaining battery level is Get higher. On the other hand, when the downside is employed, the remaining amount of the battery of the power storage device 20 can be sufficiently utilized, but there is a high risk that the remaining amount of the battery becomes empty (becomes 0).

  Actually, which value of the confidence interval is used depends on the shape of the demand, the degree of fluctuation, the form of the power receiving contract with the power company, the capacity and efficiency of the power storage device 20, and so cannot be determined in general. Determined by prior simulation. For example, in a power receiving contract with a power company, if the basic charge (monthly charge determined according to the contracted power (kW)) is low and the penalty for exceeding the contracted power (kW) is high, the forecast will rise. For example, the most economical control would be to avoid over-contracting as much as possible using, for example, a 99% upside value (a value that falls below this value with a probability of 99%). In addition, when the capacity of the power storage device 20 is large with respect to demand, the most economical control will be to actively lower the received power using the downside.

  FIG. 4 shows a case where the power storage device 20 is operated using the charge / discharge determination process according to the present embodiment for a plurality of consumers (A1, A2, B1, C1, D1) having different power usage patterns. The reduction achievement rate is calculated by changing the coefficient α of the equation (1), that is, by changing the error width α × σ (t), and the power storage device 20 is controlled based on the predicted demand. A graph comparing the times is shown. In this graph, the horizontal axis represents the coefficient α, and the vertical axis represents the reduction achievement rate. Here, the reduction achievement rate is defined as follows.

Reduction achievement rate [%]
= (Maximum demand before introduction-Maximum demand) / (Maximum demand before introduction-Maximum demand on suppression)

  When the reduction achievement rate is 100%, it indicates that the result is the same as in the case of the optimal control in which the demand can be completely predicted. As is apparent from FIG. 4, the demand pattern varies depending on the coefficient α having a negative value (in particular, α <−2.5, α <−3.0, or α <−4.0). However, it turns out that the power storage device 20 can be operated efficiently and a stable reduction achievement rate can be obtained.

  FIG. 5 is a graph illustrating an example of a result of controlling the power storage device 20 by the charge / discharge amount determination process according to the present embodiment. The past maximum power (existing maximum power) is exceeded, but the maximum power (maximum power before introduction) when not using the power storage device 20 is reduced (maximum power after introduction). Since the power storage device 20 is operated and the remaining battery level is almost used up, it can be seen that the power storage device 20 is optimally operated.

  In the above description, the case where the coefficient α for obtaining the error width α × σ (t) is fixed to a constant value has been described, but a correction value (upward value or downward value) is determined. The coefficient α need not be constant during the control period, and may be changed according to the state of the load 50 and the state of the power storage device 20. Specifically, when the remaining battery level of the power storage device 20 is high, control is performed on the active use side (downward side and the coefficient α is negative), and on the maintenance side when the remaining battery level is low. By adopting (upward side and coefficient α is a positive value), more optimal control is possible.

  Further, when determining the charge / discharge amount of the power storage device 20 with the correction value Pe ′ (t) according to the expression (1) instead of determining with the center value Pe (t) of the predicted value, in the above-described step S120 The correction value may be obtained by setting α = 0, or the step S120 for obtaining the correction value is not executed, and the charge / discharge amount of the power storage device 20 is determined using the center value of the predicted value in step S130. May be.

  Below, the main effects of the control method of the power storage device according to the present embodiment are summarized.

  1stly, the control method of the power storage device which concerns on this embodiment does not control charging / discharging of the power storage device 20 based on the conventional daily demand forecast (daily load curve), but a predetermined time interval. (For example, 30 minutes) The demand forecast is repeated sequentially, and the target value for suppressing the maximum power is calculated for the changing forecast demand in consideration of the past maximum power history and the remaining battery level, and the charge / discharge amount is calculated. By repeating the determining process, the maximum power suppression amount can be approached to be maximized.

  The pattern in which the load of each consumer uses power varies greatly depending on the day of the week, etc. (for example, the equipment does not operate on holidays, so the power used is low, and the power used does not drop during the lunch break). As described above, by using the control method of the power storage device according to the present embodiment, the predicted demand (predicted value Pe (t)) and the historical information (actual demand) for a predetermined period (for example, three months) By obtaining the error width (α × σ (t)), the power storage device 20 can be efficiently operated without considering the power usage pattern on the day of operation.

  Secondly, the control method of the power storage device according to the present embodiment does not use the predicted demand (predicted value Pe (t)) as it is, but the upswing predicted value or the downswing predicted value (correction value) as necessary. By using Pe ′ (t)), the prediction error is compensated, the risk of battery depletion for a later peak due to excessive discharge of the power storage device 20, and the maximum use of the battery by not discharging too much By balancing both of the risks that hinder the peak, it is possible to contribute to maximum peak power suppression.

DESCRIPTION OF SYMBOLS 10 Electric power storage system 20 Electric power storage apparatus 30 Electric power storage apparatus control apparatus (control apparatus)
40 system 50 load

Claims (7)

A method of controlling a power storage device that supplies power to a load,
Calculating a predicted value of power used by the load after the current time based on the actual value of power used by the load from a current time to a predetermined period before;
Determining a discharge amount of the power storage device at a current next time based on the predicted value, and
A method for controlling a power storage device, wherein the step of calculating the predicted value and the step of determining the discharge amount are repeatedly executed at predetermined time intervals. The step of calculating the predicted value calculates a center value and an error width of a predicted value of power used by the load after the current time based on the actual value, and calculates the center value and the error width of the predicted value. Is configured to calculate a corrected predicted value,
The step of determining the discharge amount is configured to determine a discharge amount of the power storage device at a current next time based on the corrected predicted value. Control method for power storage equipment. The method for controlling the power storage device according to claim 2, wherein the step of calculating the predicted value calculates the corrected predicted value by the following equation.
Pe ′ (t) = Pe (t) + α × σ (t)
However,
Pe (t): Center value of the predicted value σ (t): Standard deviation α: Coefficient α × σ (t): The error width t: Time   The method of claim 3, wherein the coefficient is a negative value.   The method of controlling a power storage device according to claim 3 or 4, wherein the coefficient is changed based on a remaining amount of the power storage device.   The power storage device control apparatus according to any one of claims 1 to 5, wherein the control method for the power storage device is mounted and discharge operation of the power storage device is controlled. A power storage device for supplying power to the load;
A power storage system comprising: the power storage device control device according to claim 6 which controls a discharge operation of the power storage device.