Electric power interchange system

Abstract

The purpose of the present invention is to appropriately set a margin of power demand prediction for use in calculation of transmission power in a power interchange system that transmits, via a power transmission network, power generated at a power generation base to a demand base. A power interchange system according to the present invention determines a correction value for demand prediction according to the absolute value of the difference between the demand prediction and an actual demand result when the difference is not within the range of an allowable difference, and applies the determined correction value to the demand prediction (see FIG. 13).

Description

Power interchange system

[0001] The present invention relates to a technology for transmitting electric power generated at a power generation base to a demand base via a power transmission network.

[0002] Self-dispatch is when a business operator with a power generation facility uses the power transmission network of the power utility to transmit power generated by the power generation facility between bases. When implementing self-dispatch, it is necessary to submit a power transmission plan to an operating organization (e.g., Organization for Cross-regional Coordination of Transmission Operators (OCCTO)) before the start of the dispatch (e.g., the day before). Furthermore, while self-dispatch is being implemented, it is necessary to transmit power as planned in advance at predetermined time intervals (e.g., 30 minutes). If the actual transmitted power deviates from the planned amount (imbalance), a penalty is generally imposed. Power transmitted from a power generation base to a demand base is sometimes called interchange power.

[0003] The following Patent Document 1 addresses the issue of "distributing electricity to a plurality of electricity consumers, including those equipped with distributed power sources, within a predetermined region (community), and balancing the supply and demand of electricity among these consumers at low cost, while stabilizing the power grid," and describes a technology that "includes an energy storage facility 6h that stores energy input to or output from a distributed power source 4 equipped in any of a plurality of electricity consumers 3a-3n within a community C, and a power demand control device 6d that allocates a predetermined amount of electricity purchased through an electricity trading device and the total amount of electricity generated by all of the distributed power sources 4 within the community C to the electricity consumers within the community C according to their respective electricity demands, and, if there is a difference between the total amount of electricity demand and the total amount of electricity supplied during the allocation, controls the operation of the distributed power sources 4 via a distributed power source control device to eliminate the difference, thereby adjusting the supply and demand of electricity" (see abstract).

[0004] The following Patent Document 2 aims to provide an electric energy control system that can comply with regulations and keep the difference between supply and demand within an allowable error range pursuant to the regulations at predetermined time intervals. The patent document describes the following technology (see abstract): "The electric energy control system of the present invention controls the difference between the amount of electricity demanded and supplied in a service area at each predetermined time interval to be equal to or less than an allowable value based on regulations. The system includes a power transmission network that supplies electric power to consumers in the service area, individual power generating units installed at the locations of the consumers in the service area, a calculation unit that calculates the amount of electricity demanded and supplied at each predetermined time interval at the consumers, and a control unit that controls the operation of the individual power generating units. The calculation unit compares the amount of actual electricity used at the consumer in a given time interval with the predicted amount of electricity demand. If the amount of actual electricity used is lower than the predicted amount of electricity demand, the control unit increases electricity consumption at the consumer, and if the amount of actual electricity used is higher than the predicted amount of electricity demand, the control unit operates the individual power generating units to supply the consumer with the shortage of electricity."

[0005] JP 2002-010500 A JP 2017-175786 A

[0006] The scheduled wheeling power can be calculated by subtracting the predicted power demand at the power generation base from the predicted value of the amount of power generated by the power generation facility, and multiplying it by a surplus capacity coefficient as necessary based on the predicted value of the power demand at the demand base. Therefore, when calculating the scheduled wheeling power, it is desirable to accurately predict the power demand at the demand base.

[0007] In power interchange, if the power transmitted from a power generation site to a demand site cannot be consumed at the demand site, a large penalty fee may be imposed. On the other hand, in recent years, power demand trends have fluctuated significantly due to the electrification and automation of transport equipment and the introduction of private power generation facilities. Furthermore, demand forecasts may be significantly off due to unexpected events such as sudden temperature changes or changes in the operation plan of private power generation facilities. Therefore, there is a high possibility that the power transmitted from a power generation site to a demand site cannot be consumed at the demand site, resulting in the imposition of a penalty fee.

[0008] In view of the above circumstances, it is considered desirable for power generation bases to secure a certain degree of margin for demand forecasts. In the prior art such as those disclosed in Patent Documents 1 and 2, such margin for demand forecasts is not sufficiently considered. This is thought to be because the possibility that interchange power cannot be consumed at demand bases is not fully considered.

[0009] The present invention has been made in consideration of the above-mentioned problems, and aims to appropriately set a margin for power demand forecasts used when calculating transmitted power in a power interchange system in which power generated at a power generation base is transmitted to a demand base via a power transmission network.

[0010] If the difference between the demand forecast and the actual demand does not fall within the range of the allowable difference, the power interchange system of the present invention determines a correction value for the demand forecast based on the absolute value of the difference and applies the determined correction value to the demand forecast.

[0011] According to the power interchange system of the present invention, in a power interchange system in which power generated at a power generation base is transmitted to a demand base via a power transmission network, it is possible to appropriately set a margin for a power demand forecast used when calculating the transmitted power. Other issues, configurations, effects, etc. will become clear from the description of the following embodiments.

[0012] 1 is a configuration diagram of a power interchange system according to a first embodiment. FIG. 1 is a diagram illustrating a process of learning a learning model stored in a storage unit 13. FIG. 2 is a diagram illustrating a process of predicting power demand using a trained learning model. FIG. 3 is a diagram illustrating a procedure for evaluating the prediction accuracy of a learning model. FIG. 4 is a diagram illustrating an example of an evaluation result of the prediction accuracy of a learning model. FIG. 5 is a diagram illustrating an error between a predicted value and an actual value of power demand over a 24-hour period. FIG. 6 is a table illustrating an allowable difference. FIG. 7 is an example of an allowable difference table stored in a storage unit 13. FIG. 8 is a diagram illustrating an example of a time-dependent change in an allowable difference. FIG. 9 is a diagram illustrating a deviation. FIG. 10 is a diagram illustrating a procedure by which an error calculation unit 112 calculates a deviation. FIG. 11 is a diagram illustrating example deviation data. FIG. 12 is a diagram illustrating a demand margin. FIG. 13 is a diagram illustrating adjustment of a demand margin. A conceptual diagram illustrating an error falling within a range of an allowable difference due to a demand margin. FIG. 14 is a flowchart illustrating a procedure by which a calculation unit 11 adjusts a demand margin. FIG. 15 is an example of a user interface provided by the calculation unit 11. FIG. 16 is a diagram illustrating a deviation in a power interchange system according to a second embodiment. 10 is a flowchart illustrating a procedure for adjusting a demand margin by a calculation unit 11 in embodiment 2. FIG. 11 is a diagram illustrating a deviation degree in a power interchange system according to embodiment 3. FIG. 12 is a flowchart illustrating a procedure for determining a demand margin at each demand base by a calculation unit 11 in embodiment 3.

[0013] <First Embodiment> Fig. 1 is a configuration diagram of a power interchange system according to a first embodiment of the present invention. The power interchange system is a system in which power generated by a supply base 1 is transmitted to a demand base 2 via a power transmission network. The demand base 2 includes power consumption equipment 21 that consumes power. The supply base 1 includes a calculation unit 11, a control unit 12, a storage unit 13, and a power supply unit 14.

[0014] The calculation unit 11 sets a margin for the predicted value of power demand at a demand base. A specific example will be described later. The calculation unit 11 includes a prediction calculation unit 111, an error calculation unit 112, a supply amount acquisition unit 113, a demand amount acquisition unit 114, and a demand margin calculation unit 115. The operation of these functional units will be described later.

[0015] The control unit 12 includes an interchange amount determination device 121 and an interchange point determination device 122. The interchange amount determination device 121 determines the amount of power to be transmitted to the demand base 2 based on the power demand forecast value corrected using the demand margin set by the calculation unit 11. When there are multiple demand bases 2, the interchange point determination device 122 determines which of the demand bases 2 is to be the power transmission destination.

[0016] The storage unit 13 stores a learning model that has been previously subjected to machine learning to predict the power demand at the demand base 2. The storage unit 13 also stores data that describes an allowable difference, which will be described later. The power supply unit 14 transmits the power generated at the supply base 1 to the demand base 2.

[0017] FIG. 2A is a diagram illustrating the process of learning the learning model stored in the memory unit 13. The prediction calculation unit 111 inputs data describing past parameters at the demand base 2 (e.g., parameters that may affect the demand forecast, such as temperature, humidity, day of the week, and past demand results) to the learning model. The learning model calculates a predicted value of power demand by weighting the input data. The prediction calculation unit 111 calculates a prediction error by comparing the predicted value and actual value of power demand. The prediction calculation unit 111 updates the weighting so as to minimize the prediction error. The learning model can be trained by repeating this process. A known cognitive technique such as backpropagation can be used as the learning algorithm.

[0018] 2B is a diagram illustrating the process of predicting power demand using a trained learning model. The prediction calculation unit 111 inputs data similar to that shown in FIG. 2A for the day on which the prediction is to be performed into the learning model. The learning model calculates a predicted value of power demand by weighting the input data. The prediction calculation unit 111 obtains the predicted value.

[0019] FIG. 3 is a diagram illustrating the procedure for evaluating the prediction accuracy of a learning model. The error calculation unit 112 performs the evaluation according to this procedure using past weather data and actual power demand. First, the explanatory variables of the evaluation results and the evaluation period are determined. The evaluation is performed by inputting the data to be evaluated into the learning model and calculating the error between the predicted value and the actual value over the evaluation period. The evaluation results are stored in the memory unit 13. The explanatory variables are data items of the learning data input into the learning model when training the learning model. The evaluation period is a period during which data suitable for use as learning data can be obtained, such as the "convergence 1" period described below.

[0020] FIG. 4 illustrates the results of evaluating the prediction accuracy of a learning model. The absolute error between the predicted and actual values ​​of power demand converges within a certain range during the evaluation period. This absolute error after convergence is designated "convergence 1" in FIG. 4. On the other hand, there are times during the evaluation period when the absolute error temporarily increases. This tendency is particularly evident at demand centers where power demand fluctuates greatly due to the circumstances described above. This temporarily increased absolute error is designated "convergence 2" in FIG. 4.

[0021] Convergence 2 also converges within a certain range over the long term. This is shown in Figure 4 by the peak of convergence 2 gradually decreasing. However, even though it gradually decreases over the long term, it is not desirable to use convergence 2 in order to always ensure the accuracy of demand forecasting. Therefore, in reality, the only measurement data that can be used to forecast electricity demand at such demand bases is convergence 1. In other words, at demand bases where electricity demand fluctuates greatly, the data that can be used as basic data for demand forecasting is limited.

[0022] Fig. 5 is a diagram illustrating an example of the error between the predicted value and the actual value of power demand over a 24-hour period. The absolute difference between the upper and lower limits of the error is defined as the absolute error. In addition to the long-term convergence tendency of the error as explained in Fig. 4, the error range of the power demand forecast tends to be highly dependent on the demand base.

[0023] Fig. 6 is a table illustrating the allowable difference. At a demand site where electricity demand fluctuates greatly, the period suitable for acquiring data (i.e., explanatory variables) to be input to the learning model is limited, as explained in Fig. 4. Here, it is assumed that 10 weeks' worth of data is acquired.

[0024] In the first three weeks of the ten weeks, the learning results have not yet converged sufficiently, so it is assumed that there will be a large error between the predicted and actual values. Therefore, the allowable difference allowed for error during this period is set to a somewhat large value (20% or more in this example). In the next four weeks (weeks 4-7), the learning results are expected to have converged sufficiently, so the allowable difference is set to a small value (3-7% in this example). The error does not necessarily decrease as the amount of available data increases; in fact, there are cases where the error actually increases, as in the case of "Convergence 2" described in Figure 4. This applies to the final two weeks (weeks 8-10), where the allowable difference is slightly increased.

[0025] Figure 7 shows an example of an allowable difference table stored in the storage unit 13. The allowable difference described in Figure 6 tends to differ depending on the period length for which data suitable for input to the learning model can be obtained (i.e., the period length of the available explanatory variables), so the allowable difference table also defines the allowable difference for each period length. Here, data examples for period lengths of 15 weeks, 5 weeks, and 5 days are shown. The data structure for each period length is the same as that shown in Figure 6.

[0026] The allowable difference table can be created by calculating the error between the demand forecast and the actual demand over the period in which the explanatory variables are acquired, and determining the allowable difference for that error for each period within the acquisition period (for example, if the acquisition period is 15 weeks, for each period of each of patterns A to E in FIG. 7). The error may be calculated by the calculation unit 11 or by any other appropriate means. The allowable difference can be determined so that it decreases over time within the acquisition period, while taking into account a temporary increase in error such as convergence 2. The calculation unit 11 may determine the allowable difference according to these rules, or the user may determine it manually.

[0027] FIG. 8 is a diagram illustrating an example of the change in the allowable difference over time. It is expected that the error between the predicted and actual power demand values ​​will decrease over time. Therefore, the allowable difference, which is the error allowed between the two, will also gradually decrease over time. Since the allowable difference is a value with a range, as shown in FIG. 8, the allowable difference at each point in time has a numerical range at that time. Both the median of the allowable difference and the range of the allowable difference itself will gradually decrease over time. However, during periods when the error temporarily increases, such as in "Convergence 2," the allowable difference may also temporarily increase.

[0028] FIG. 9 is a diagram illustrating the degree of deviation. The error calculation unit 112 calculates the absolute value of the error (absolute error) between the predicted value and the actual value of the power demand for a specific day (the implementation day in FIG. 9 ). The error calculation unit 112 further identifies the median of the allowable difference for the same day (the average of the upper and lower limits of the allowable difference). The error calculation unit 112 calculates the absolute difference between the absolute error and the median as the degree of deviation. The use of the degree of deviation will be described later.

[0029] FIG. 10 is a diagram illustrating the procedure by which the error calculation unit 112 calculates the deviation. First, the implementation date described in FIG. 9 is identified, and the error between the predicted value and the actual value of the power demand on that day is calculated. The allowable difference table described in FIG. 7 is obtained from the storage unit 13. The error calculation unit 112 identifies which error pattern in the allowable error table the calculated error corresponds to. For example, the error pattern can be identified using the elapsed time from the point in time when the data to be input to the learning model began to be acquired (e.g., if the period during which explanatory variables can be used is 15 weeks and the implementation date is the 9th week, the error pattern is C_15w). The error calculation unit 112 determines whether the error falls within the allowable difference range of the identified error pattern. If the error is outside the allowable difference range, the deviation is calculated using the procedure described in FIG. 9.

[0030] Fig. 11 shows an example of deviation data. The error calculation unit 112 stores the deviation calculated by the procedure of Fig. 10 as deviation data in the storage unit 13. The deviation data can be written in the same format as the allowable difference table by adding further deviations.

[0031] 12 is a diagram illustrating the demand margin. The power interchange system determines the power to be transmitted to the demand base 2 based on the power demand forecast value. However, rather than using the demand forecast value as is, a small margin is subtracted from the demand forecast value so that the interchange power can be reliably consumed at the demand base 2, and the transmitted power is determined based on the demand amount after the subtraction.

[0032] Fig. 13 is a diagram showing how the demand margin is adjusted. The demand margin calculation unit 115 sets the demand margin described in Fig. 12 by, for example, multiplying the demand forecast value by a predetermined rate. If the demand forecast value after subtracting the demand margin does not fall within the range of the allowable difference, the demand margin calculation unit 115 further adjusts the demand margin to bring the demand forecast value within the range of the allowable difference.

[0033] Specifically, the demand margin can be adjusted as follows. First, to ensure that the demand base 2 can consume the power transmitted from the supply base 1, the maximum value of power demand during the period in which power interchange is implemented needs to be greater than (or the same as) the maximum value of the interchanged power during that period. Therefore, the demand margin is set so that the maximum value of the demand forecast during that period is greater than the maximum value of the interchanged power during that period. Then, the demand margin is adjusted so that the error between the demand forecast and the actual demand falls within the range of the allowable difference corresponding to that period (i.e., the error is adjusted so that it is equal to or less than the upper limit of the allowable difference). As long as these conditions are met, the amount of adjustment of the demand margin can be arbitrary. Through these adjustments, the possibility that the demand base 2 can consume the interchanged power can be maintained higher than before the correction value was applied, while the error can be kept within the range of the allowable difference.

[0034] If the demand forecast value is lower than (or the same as) the interchangeable power, there is a possibility that if electricity is transmitted to the demand base 2, the electricity cannot be consumed at the demand base 2. Therefore, in such a case, it is desirable to set the interchangeable power to 0 or to a small value equal to or lower than the reference value, which has a sufficiently high possibility of being consumed at the demand base 2.

[0035] 14 is a conceptual diagram showing how the demand margin keeps the error within the range of the allowable difference. In general, the greater the absolute error deviates from the median of the allowable difference (i.e., the greater the deviation), the greater the adjustment amount of the demand margin needs to be.

[0036] FIG. 15 is a flowchart illustrating the procedure by which the calculation unit 11 adjusts the demand margin. The demand margin calculation unit 115 acquires the deviation calculated by the error calculation unit 112 and the allowable difference for the period from the storage unit 13. The demand margin calculation unit 115 calculates an initial value of the demand margin based on, for example, the magnitude of the demand forecast value. The supply amount acquisition unit 113 and the demand amount acquisition unit 114 acquire the maximum value of the demand forecast value and the maximum value of the interchanged power for the period, respectively. The demand margin calculation unit 115 adjusts the demand margin according to the procedure described in FIG. 13 and stores the result in the storage unit 13. The interchange point determination device 122 may determine the priority of the demand points to transmit power, for example, according to the procedure described in a third embodiment described below. The interchange amount determination device 121 determines the power to be transmitted to each demand point according to the priority.

[0037] Fig. 16 is an example of a user interface provided by the calculation unit 11. The user interface can present at least any of the parameters acquired by the calculation unit 11 through the above procedure. For example, parameters such as predicted power demand, actual power demand, the difference between these, the allowable difference, and the power transmitted to the demand base can be presented. The graph in the lower part of Fig. 16 shows the predicted and actual power demand values ​​and the difference between them.

[0038] <Second embodiment> Fig. 17 is a diagram illustrating the deviation in a power interchange system according to a second embodiment of the present invention. In the first embodiment (Fig. 9), it has been explained that the deviation is the absolute difference between the absolute error of the power demand and the median of the allowable difference. In the second embodiment, it is assumed that the demand base 2 is equipped with a solar cell, and the deviation is corrected (or updated) by taking into account the output fluctuation of the solar cell.

[0039] The photovoltaic output can be used to cover the power demand at the demand base 2. Therefore, the predicted value of power demand needs to be calculated taking into account the photovoltaic output. However, since the photovoltaic output fluctuates over time, this fluctuation needs to be taken into account. In other words, the deviation described in the first embodiment also needs to be calculated taking into account the fluctuation in the photovoltaic output. For example, when calculating the error between the demand forecast value and the actual demand value, the calculation can be performed after adding the maximum fluctuation range of the photovoltaic output.

[0040] FIG. 18 is a flowchart illustrating the procedure for adjusting the demand margin performed by the calculation unit 11 in the second embodiment. In addition to the procedure described in the first embodiment, the calculation unit 11 acquires the output fluctuation range of the solar cell. This value can be acquired, for example, from a history of output fluctuation ranges in similar weather conditions in the past. The calculation unit 11 recalculates the error (and the degree of deviation) by adding the maximum fluctuation range of the solar cell output to the error between the demand forecast and the actual demand. The other procedures are the same as those in the first embodiment.

[0041] <Third embodiment> Fig. 19 is a diagram illustrating the degree of deviation in a power interchange system according to a third embodiment of the present invention. When there are multiple demand bases 2, the degree of deviation can be calculated for each demand base. Fig. 19 shows an example in which calculations are made for three demand bases. For base (1), the predicted value and actual value nearly match, so the degree of deviation is almost 0%. For base (2), the degree of deviation is within the allowable difference range, so the demand margin also falls within that range. For base (3), the degree of deviation exceeds the allowable difference range, so the demand margin needs to be significantly adjusted.

[0042] FIG. 20 is a flowchart illustrating the procedure by which the calculation unit 11 determines the demand margin at each demand base in the third embodiment. The calculation unit 11 calculates the deviation for each demand base in the same manner as in the first embodiment. The calculation unit 11 sets a larger demand margin as the deviation increases. In the example described in FIG. 19, base (1) has the smallest demand margin, and base (3) has the largest.

[0043] The calculation unit 11 may further determine the power transmission destination by assigning higher priorities to demand bases with lower deviations (or demand margins) and transmitting power in order of priority. For example, the following determination procedure may be considered: (a) Allocate transmission power to demand bases with smaller deviations, and if there is surplus generated power, allocate transmission power to the demand base with the next smallest deviation. This procedure is repeated until there is no more transmittable power. (b) Determine the power to be transmitted to each demand base such that the smaller the deviation, the higher the fulfillment rate for power demand. The calculation unit 11 may not perform power interchange for bases with lower priorities (bases with errors exceeding a threshold) regardless of the demand forecast.

[0044] <Regarding Modifications of the Present Invention> The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0045] In the above embodiment, any known technology can be used as the learning algorithm used by the calculation unit 11 to predict the power demand.

[0046] In the above embodiment, if the calculation unit 11 can control the power consumption equipment 21 provided in the demand base 2, the deviation may be kept within the range of the allowable difference. That is, if the actual power demand exceeds the predicted power demand, the power consumption may be reduced, and if the prediction exceeds the actual power demand, the power consumption may be increased.

[0047] In the above embodiment, each functional unit (e.g., the calculation unit 11, the control unit 12, etc.) provided in the supply base 1 can be configured by hardware such as a circuit device that implements these functions, or can be configured by a calculation device such as a CPU (Central Processing Unit) that executes software that implements these functions.

[0048] 1: Supply base 11: Calculation unit 12: Control unit 13: Storage unit 14: Power supply unit 2: Demand base

Claims

1. A power interchange system which transmits power generated at a power generation base to a demand base via a power transmission network, comprising: a calculation unit which predicts power demand at the demand base; and a memory unit which stores data describing an allowable difference that is permitted as a difference between a predicted value and an actual value of the power demand, wherein if the difference is not within the range of the allowable difference, the calculation unit determines a correction value for the predicted value in accordance with an absolute value of the difference, and corrects the predicted value by applying the determined correction value to the predicted value, and the calculation unit determines the power to be transmitted to the demand base based on the predicted value corrected using the correction value.

2. The power interchange system of claim 1, characterized in that, when the difference is equal to or greater than an upper limit of the allowable difference, the calculation unit determines a value to be subtracted from the predicted value as the correction value, and when the difference is equal to or less than a lower limit of the allowable difference, the calculation unit sets the power to be transmitted to the demand base to 0 or a reference value or less.

3. The power interchange system described in claim 1, characterized in that the calculation unit determines the correction value so that the predicted value is greater than the power, thereby increasing the possibility that the power demand specified by the predicted value can be consumed at the demand base more than before the correction value is applied.

4. The power interchange system described in claim 1, characterized in that the data describes the allowable difference for each period within a period for which the calculation unit predicts the power demand, and the calculation unit obtains from the data the allowable difference corresponding to the time during the period when power is transmitted to the demand base, and determines the correction value using the obtained allowable difference.

5. The power interchange system described in claim 1, characterized in that the data is constructed by calculating the difference over a specified period and determining the allowable difference over the specified period based on the calculated difference, the data defines the allowable difference for each length of the specified period, and the calculation unit obtains from the data the allowable difference corresponding to the length of the target period for which the process of determining the power is performed, and determines the correction value using the obtained allowable difference.

6. The power interchange system according to claim 1, characterized in that the demand base is configured to generate power using solar cells, and the calculation unit recalculates the difference by adding fluctuations in the amount of power generated by the solar cells to the predicted value.

7. The power interchange system according to claim 1, characterized in that the calculation unit determines the power transmission destination so as to give priority to the demand base to which the difference is smaller.

8. The power interchange system according to claim 1, characterized in that the calculation unit does not transmit the power to the demand base where the difference exceeds a threshold value, regardless of the predicted value.

9. The power interchange system of claim 6, characterized in that the calculation unit determines the amount of power to be transmitted to each of two or more demand bases, and the calculation unit determines the power transmission destination so as to transmit the power in order from the demand base with the smallest difference, and if there is a surplus of power generation, to transmit the power to the demand base with the next smallest difference.

10. The power interchange system of claim 6, characterized in that the calculation unit determines the power to be transmitted to each of two or more of the demand bases, and the calculation unit determines the power to be transmitted to each of the demand bases in order from the demand base with the smallest difference so that the fulfillment rate for the power demand becomes greater.

11. The power interchange system according to claim 1, characterized in that the calculation unit provides a user interface, and the user interface presents at least one of the predicted value, the actual value, the difference, the allowable difference, and the power.

12. The power interchange system of claim 1, characterized in that the demand base is equipped with power consumption equipment that consumes the power demand, and the calculation unit adjusts the power consumed by the power consumption equipment so that the difference falls within the range of the allowable difference.

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