Patent Publication Number: US-2016232458-A1

Title: Storage battery charge/discharge planning device, storage battery charge/discharge planning method, program, and storage battery charging/discharging device

Description:
TECHNICAL FIELD 
     The present invention relates to a storage-battery charge/discharge planning device, a method for planning charge/discharge of the storage battery, a program, and a storage-battery charge/discharge device. 
     BACKGROUND ART 
     For example, there has been known a charge/discharge device that controls charging and discharging of a storage battery (for example, Patent Document 1). 
     CITATION LIST 
     Patent Document 
     Patent Document 1: Japanese Patent Application Laid-open Publication No. 2011-244682 
     SUMMARY OF INVENTION 
     Technical Problem 
     For example, the charge/discharge device in Patent Document 1 controls charge and discharge of the storage battery based on a result of comparison between a sale price and a reference price of electric power. This control performed by the charge/discharge device, however, does not consider the charge/discharge efficiency of the storage battery. Thus, when the storage battery is charged and discharged by the charge/discharge device, economic advantages that is to be brought by virtue of charging and discharging of the storage battery may not be provided. 
     Solution to Problem 
     In order to solve the above-described problems, a primary aspect of the invention is directed to a storage-battery charge/discharge planning device, including: a judging device configured to judge economic efficiency to be brought by charging and discharging of a storage battery, based on a first sale price of electric power in a first time slot, a second sale price of the electric power in a second time slot, and charge/discharge efficiency of the storage battery, the first time slot being obtained by dividing a day into predetermined time periods, the second time slot being obtained by dividing the day into the predetermined time periods and being different from the first time slot; and a determining device configured to determine a charge/discharge plan of the storage battery in the first and the second time slots based on a judgment result of the judging device. 
     Other features of the present invention will become apparent from descriptions of the accompanying drawings and of the present specification. 
     Advantageous Effects of Invention 
     According to the present invention, a charge/discharge plan of a storage battery can be determined, considering economic efficiency to be brought by charge and discharge of a storage battery performed based on charge/discharge efficiency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a distribution system according to first to third embodiments of the present invention. 
         FIG. 2  is a block diagram illustrating hardware of a charge/discharge control device of the first to third embodiments according to the present invention. 
         FIG. 3  is a block diagram illustrating the charge/discharge control device according to the first to third embodiments of the present invention. 
         FIG. 4  is a graph illustrating first price information according to the first embodiment of the present invention. 
         FIG. 5  is a diagram illustrating the first price information according to the first embodiment of the present invention. 
         FIG. 6  is a diagram illustrating second price information according to the first embodiment of the present invention. 
         FIG. 7  is a diagram illustrating a correspondence table according to the first embodiment of the present invention. 
         FIG. 8  is a diagram illustrating charge/discharge plan information according to the first embodiment of the present invention. 
         FIG. 9  is a flowchart illustrating an operation of a planning unit according to the first embodiment of the present invention. 
         FIG. 10  is a flowchart illustrating an operation of the charge/discharge control device according to the first embodiment of the present invention. 
         FIG. 11  is a flowchart illustrating an operation of a planning unit according to the second embodiment of the present invention. 
         FIG. 12  is a flowchart illustrating an operation of a planning unit according to the third embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     At least the following matters will become apparent from descriptions of the present specification and of the accompanying drawings. 
     First Embodiment 
     Distribution System 
     Hereinafter, a distribution system according to an embodiment of the present invention will be described with reference to  FIG. 1 .  FIG. 1  is a diagram illustrating the distribution system according to an embodiment of the present invention. A plurality of consumers having configurations similar to a configuration of a consumer  10  are coupled to a distribution line L 1 . However, for convenience of explanation, only the single consumer  10  is illustrated. 
     A distribution system  100  is an electric power system to supply electric power to a load R 1 . The distribution system  100  includes a distribution transformer  101 , the distribution line L 1 , and the consumer  10 . 
     The distribution transformer  101  is a device that transforms a voltage on a primary side at a predetermined transformer ratio, to output the transformed voltage from a secondary side. Electric power is supplied from a power-transmission line to the primary side of the distribution transformer  101 . One end of the distribution line L 1  is coupled to the secondary side of the distribution transformer  101 : The distribution line L 1  extends downstream from the upstream one end thereof which is coupled to the secondary side of the distribution transformer  101 . 
     The consumer  10  is, for example, an ordinary household to which electric power is supplied from the distribution line L 1  and from which electric power is supplied to the distribution line L 1 . The consumer  10  includes a measuring device M 1  (receiving device), a charge/discharge device  11 , a storage battery  12 , the load R 1 , and a charge/discharge control device  3  (storage battery charge/discharge device). 
     The load R 1  is an electric power load that operates based on the electric power supplied from the distribution line L 1  or the like. 
     The measuring device M 1  is, for example, a smart meter that measures the electric power supplied from the distribution line L 1  to the consumer  10  and measure the electric power supplied from the consumer  10  to the distribution line L 1 . Moreover, the measuring device M 1  receives first price information S 1  from, for example, an electric power supplier (not illustrated). The first price information S 1  is information indicative of a price of electric power. The details of the first price information S 1  will be described later. 
     The storage battery  12  is a storage battery that is charged with the electric power supplied from the distribution line L 1 , and is discharged to supply the electric power to the distribution line L 1 . 
     The charge/discharge device  11  is a device that charges and discharges the storage battery  12  in response to a control signal Ct. 
     The charge/discharge control device  3  plans charge and discharge of the storage battery  12  based on the first price information S 1 , which is received by the measuring device M 1 . The charge/discharge control device  3  outputs the control signal Ct based on the plan of charge and discharge of the storage battery  12 . 
     Charge/Discharge Control Device 
     Hereinafter, a distribution system according to an embodiment of the present invention will be described with reference to  FIGS. 2 and 3 .  FIG. 2  is a block diagram illustrating hardware of the charge/discharge control device according to an embodiment of the present invention.  FIG. 3  is a block diagram illustrating the charge/discharge control device according to an embodiment of the present invention. 
     The charge/discharge control device  3  includes a Central Processing Unit (CPU)  31 , a communication device  32 , a storage device  33 , a display device  34 , and an input device  35 . The CPU  31  executes a program stored in the storage device  33 , to perform various functions of the charge/discharge control device  3 , and integrally control the charge/discharge control device  3 . The storage device  33  stores the above-described program and various pieces of information. The display device  34  is a display that displays information of the charge/discharge control device  3 . The input device  35  is, for example, a keyboard and a computer mouse through which information is input to the charge/discharge control device  3 . The communication device  32  performs communications between the measuring device M 1  and the charge/discharge device  11 . 
     The charge/discharge control device  3  further includes a planning unit  36  (judging device, determining device, and storage-battery charge/discharge planning device) and a control unit  37  (also referred to as “various functions of the charge/discharge control device  3 ”). Note that the various functions of the charge/discharge control device  3  are realized by execution of the program stored in the storage device  33  by the CPU  31 . 
     The planning unit  36  creates charge/discharge plan information S 3  ( FIG. 8 ) based on the first price information S 1 . The control unit  37  (control device) causes the control signals Ct to be output based on the charge/discharge plan information S 3 . The details of the planning unit  36  and the control unit  37  will be described later. 
     First Price Information 
     Hereinafter, the first price information according to an embodiment of the present invention will be described with reference to  FIGS. 4 and 5 .  FIG. 4  is a graph illustrating the first price information according to an embodiment of the present invention.  FIG. 5  is a diagram illustrating the first price information according to an embodiment of the present invention. 
     The first price information S 1  indicates planned values of electric power prices in future based on real-time pricing. Note that the real-time pricing means, for example, an electric power rate system where electric power prices vary by time slot of e.g., one hour during a day. The electric power price means a price of electric power supplied from the consumer  10  to the distribution line L 1  (also referred to as a “electric power for sale”) and a price of the electric power supplied from the distribution line L 1  to the consumer  10  (also referred to as a “electric power for purchase”). In the first price information S 1 , the prices of the electric power for sale and the prices of the electric power for purchase are the same. That is, the first price information S 1  indicates that both the price of the electric power for sale in the time slot B 1  and the price of the electric power for purchase in the time slot B 1  are A 1 , and other information. 
     In the first price information S 1 , the time slots are associated with the planned values of the electric power prices, respectively. That is, the first price information S 1  includes a plurality of combinations of the time slots and the planned values of the electric power prices which are associated with these time slots. The first price information S 1  indicates that the planned value of the electric power price (referred to as a “planned electric power price”) in the time slot B 1 , which is from 12 a.m. to 1 a.m., is A 1 , the planned electric power price in the time slot B 2 , which is from 1 a.m. to 2 a.m., is A 2 , and the planned electric power price in the time slot B 3 , which is from 2 a.m. to 3 a.m., is A 3 . Further, the first price information S 1  indicates that the planned electric power price in the time slot  320 , which is from 7 p.m. to 8 p.m., is A 20 , the planned electric power price in the time slot  521 , which is from 8 p.m. to 9 p.m., is A 21 , and the planned electric power price in the time slot B 22 , which is from 9 p.m. to 10 p.m., is A 22 . 
     Note that the first price information S 1  in  FIG. 5 , for example, includes the planned electric power prices for 24 hours. However, for convenience of explanation, the description of the planned electric power prices in time slots other than the time slots B 1  to B 3  and B 20  to B 22  is omitted. 
     Planning Unit 
     Hereinafter, the planning unit according to an embodiment of the present invention will be described with reference to  FIGS. 5 to 9 .  FIG. 6  is a diagram illustrating second price information according to an embodiment of the present invention. Note that second price information S 2  includes information corresponding to Nos. 1 to 24. However, for convenience of explanation, the description of information corresponding to Nos. 4 to 21 is omitted.  FIG. 7  is a diagram illustrating a correspondence table according to an embodiment of the present invention.  FIG. 8  is a diagram illustrating charge/discharge plan information according to an embodiment of the present invention.  FIG. 9  is a flowchart illustrating an operation of the planning unit according to an embodiment of the present invention. 
     &lt;Outline&gt; 
     The planning unit  36 , after rearranging the first price information S 1 , selects a pair of time slots to set a charge/discharge plan in the selected pair of time slots. The planning unit  36  sets the charge/discharge plan, for example, of all the time slots for 24 hours in the first price information S 1 . The planning unit  36  creates charge/discharge plan information S 3  in which the settings of the charge/discharge plan have been reflected. 
     &lt;Detail&gt; 
     The planning unit  36  obtains the first price information S 1  (Step St 11 ). The planning unit  36  sorts the combinations of the time slots and the planned electric power prices, which correspond to these time slots, in the first price information S 1 , in the order of ascending planned electric power prices, to create the second price information S 2  (Step St 12 ). In the second price information S 2 , the lowest planned electric power price combination is associated with No. 1, and the highest planned electric power price combination is associated with No. 24. 
     The planning unit  36  sets 1 as a value of a variable K (Step St 13 ). Note that the variable K is used to select a pair of planned electric power prices from the second price information S 2 . The values of the variable K correspond to numbers indicated in the second price information S 2 . 
     The planning unit  36  selects a pair of planned electric power prices from the second price information S 2  based on the value of the variable K being 1. Note that the planning unit  36  selects a pair of planned electric power prices from the second price information S 2  based on the value of the variable K and a correspondence table T 1 . In the correspondence table T 1 , the values of the variable K are associated with the numbers in the second price information S 2 . 
     Specifically, the planning unit  36  selects A 3 , which corresponds to No. 1 in the second price information S 2 , and A 21 , which corresponds to No. 24. Note that, when the value of the variable K is 2, A 2 , which corresponds to No. 2 in the second price information S 2 , and A 20 , which corresponds to No. 23, are selected. Alternatively, when the value of the variable K is 3, A 1  which corresponds to No. 3 in the second price information S 2 , and A 22  which corresponds to No. 22, are selected. When the values of the variable K are 4 to 12, the planned electric power prices are selected similarly to the cases where the values of the variable K are 1 to 3. 
     The planning unit  36  calculates a charge/discharge price ratio based on the selected pair of planned electric power prices. Specifically, the planning unit  36  employs, as the charge/discharge price ratio when the value of the variable K is 1, a result of division performed using A 3 , which is a lower one of the pair of planned electric power prices, as a dividend, and A 21 , which is a higher planned electric power price, as a divisor. 
     C k  and C 24-(k-1)  at Step St 14  correspond to the planned electric power price in the second price information S 2 . The “k” in C k  and C 24-(k-1)  corresponds to the variable K. For example, when the value of the variable K is 1, C k  at Step St 14  is C 1  and C 24-(k-1)  is C 24 . At this time, the index of C corresponds to a number in the second price information S 2 . Accordingly, C 1  and C 24  indicate A 3  and A 21  in the second price information S 2 , respectively. That is, for example, when the value of the variable K is 1, C k  indicates A 3 , and C 24-(k-1)  indicates A 21 . Further, for example, when the value of the variable K is 2, C k  indicates A 2 , and C 24-(k-1)  indicates A 20 . 
     The planning unit  36  determines (judges) whether the charge/discharge price ratio is smaller than charge/discharge efficiency of an electricity storage system (also referred to as “charge/discharge efficiency”) or not (Step St 14 ). 
     The charge/discharge efficiency is a product of charge efficiency p when the storage battery  12  is charged with electric power and discharge efficiency q when the storage battery  12  charged with electric power is discharged. For example, the charge efficiency p of 0.9 means that, when the electric power of 1 (kWh) is supplied to the storage battery  12 , electric power corresponding to 0.9 (kWh), which is equivalent to 0.9 times of 1 (kWh), is charged. Further, for example, the discharge efficiency q of 0.9 Means that, when the electric power corresponding to 1 (kWh) has been charged to the storage battery  12  and the electric power charged to the storage battery  12  is all discharged, the electric power of 0.9 (kWh), which is equivalent to 0.9 times of 1 (kWh), is output from the storage battery  12 . 
     Step St 14  determines whether or not the charging and discharging of the storage battery  12  in the time slot corresponding to the selected pair of planned electric power prices bring an economic advantage for the consumer  10 . For example, the following describes an example of the economic advantage in the case where the charge efficiency p is 0.9 and the discharge efficiency q is 0.89. 
     For example, in order to output electric power of 1 (kWh), the electric power corresponding to 1.125 (kWh) (corresponding to 1 (kWh) 0.89) needs to be charged to the storage battery  12 . In order to charge the electric power corresponding to 1.125 (kWh) to the storage battery  12 , electric power corresponding to 1.25 (kWh) (corresponding to 1.125 (kWh)=0.9) needs to be supplied to the storage battery  12 . In this occasion, for example, in the case where electricity is sold by discharging the storage battery  12  at the time of the planned electric power price of 12.5 yen, and considering that the charge/discharge efficiency is about 0.8 (0.9×0.89), the economic advantages are to be brought when the electricity of 1.25 (kWh) is purchased at the time of the planned electric power price of 10 yen or less and the storage battery  12  is charged with this electric power. 
     Note that “selling electricity” means that the consumer  10  supplies electric power to the distribution line L 1  to sell this electric power to electric power companies or the like. When the electricity is sold, the electric power company pays consideration to the consumer  10  based on the electric power price, the sold electric energy, etc. “Purchasing electricity” means that the consumer  10  purchases electric power from the electric power company or the like so that the electric power is supplied from the distribution line L 1 . When the electricity is purchased, the consumer  10  pays consideration to the electric power company based on the electric power price, the purchased electric energy, etc. When a difference value of the price paid in purchasing electricity with respect to the price that the consumer  10  obtains in selling electricity is, for example, larger than a predetermined value (e.g., 0), the economic advantage is to be provided by charging and discharging the storage battery  12 . If this difference value is smaller than the predetermined value (e.g., 0), the economic advantage is not to be provided by charging and discharging the storage battery  12 . 
     For example, when it is determined (judged) at Step St 14  that the charge/discharge price ratio is smaller than the charge/discharge efficiency (YES at Step St 14 ), the planning unit  36  sets a charge control or a discharge control in the time slot corresponding to the selected pair of planned electric power prices, considering that the economic advantage for the consumer  10  will be provided. Specifically, the planning unit  36  sets charge control in the time slot B 3  corresponding to A 3  which is a lower one of the pair of planned electric power prices, and sets discharge control in the time slot B 21  corresponding to A 21  which is a higher planned electric power price (Step St 15 ). At this time, the planning unit  36  reflects the setting results in the charge/discharge plan information S 3 . 
     Meanwhile, for example, when it is determined (judged) at Step St 14  that the charge/discharge price ratio is smaller than the charge/discharge efficiency (NO at Step St 14 ), the planning unit  36  sets stop control in both the time slots corresponding to the selected pair of planned electric power prices, considering that the economic advantage for the consumer  10  will not be provided (Step St 17 ). At this time, the planning unit  36  reflects the setting results in the charge/discharge plan information S 3 . Note that the charge control means charging the storage battery  12 , the discharge control means discharging the storage battery  12 , and the stop control means that neither charging nor discharging of the storage battery  12  is executed. 
     That is, at Step St 14 , the planning unit  36  judges the economic efficiency (economic advantage) to be brought by charging and discharging of the storage battery  12 . Then, the planning unit  36  determines the charge/discharge plan in the time slot corresponding to the pair of planned electric power prices, based on this judgment result of the economic efficiency. 
     The planning unit  36  determines whether the value of the variable K is 12 or not (Step St 16 ). For example, when the planning unit  36  determines that the value of the variable K is not 12 (NO at Step St 16 ), the planning unit  36  adds 1 to the value of the variable K (Step St 18 ) and executes the determination at Step St 14  again, considering that the control has not yet been set to all the time slots in the second price information S 2 . Meanwhile, for example, when the planning unit  36  determines that the value of the variable K is 12 (YES at Step St 16 ), the planning unit  36  ends the operation considering that the control has been set to all the time slots in the second price information S 2 . 
     When the planning unit  36  ends the operation, the charge/discharge plan information S 3  is to have been created. The charge/discharge plan information S 3  indicates that the storage battery  12  is controlled so as to be charged and discharged in the time slots B 1  and B 20 , respectively, and the storage battery  12  is neither charged nor discharged in the time slot B 9 , and other information. 
     Note that the storage device  33  may store information indicative of the first price information S 1 , the second price information S 2 , the charge/discharge plan information S 3 , and the correspondence table T 1 . 
     Control Unit 
     Hereinafter, the control unit according to an embodiment of the present invention will be described with reference to  FIG. 8 . 
     The control unit  37  causes the control signal Ct to be output based on the charge/discharge plan information S 3  and the current time slot. The control unit  37  causes the control signal Ct corresponding to the current time slot to be output. 
     For example, when the current time slot is the time slot  21 , the control unit  37  causes the control signal Ct for charging the storage battery  12  to be output. At this time, the charge/discharge device  11  charges the storage battery  12  with the purchased electric power, which is supplied from the distribution line L 1  to the consumer  10 . 
     Alternatively, for example, when the current time slot is the time slot  29 , the control unit  37  causes the control signal Ct for neither charging nor discharging the storage battery  12  to be output. At this time, the charge/discharge device  11  electrically disconnects the storage battery  12  from the distribution line L 1  and the load R 1 , to stop charge and discharge of the storage battery  12 . 
     Alternatively, for example, when the current time slot is the time slot B 20 , the control unit  37  causes the control signal Ct for discharging the storage battery  12  to be output. At this time, the charge/discharge device  11  discharges the storage battery  12  and supplies the electric power output by such discharge to the distribution line L 1 , to sell the electricity. Note that, at this time, the storage battery  12  may be electrically disconnected from the load R 1 , such that all the electric power discharged from the storage battery  12  is supplied to the distribution line L 1 . 
     Operation 
     Hereinafter, an operation performed by the charge/discharge control device according to an embodiment of the present invention will be described with reference to  FIGS. 1 to 8 , and  FIG. 10 .  FIG. 10  is a flowchart illustrating an operation of the charge/discharge control device according to an embodiment of the present invention. It is assumed that the variable t indicates a time slot in a day during which the charge/discharge control device  3  performs control. For example, it is assumed that the variable t of the value of 1, 2, 3, or the like indicates the time slot B 1 , B 2 , B 3 , or the like, respectively. 
     As described above, the charge/discharge control device  3  creates the charge/discharge plan information S 3  (Step St 20 ). The charge/discharge control device  3 , for example, creates the charge plan information S 3  on the previous day of performing the operations of Steps St 21  to St 24 . 
     The charge/discharge control device  3  sets 1 as the value of the variable t (Step St 21 ). This indicates that the current time slot is the time slot B 1  in the charge/discharge plan information S 3 . The charge/discharge control device  3  performs control according to the time slot corresponding to the value of the variable t (Step St 22 ). Specifically, for example, when the value of the variable t is 1, the charge/discharge control device  3  performs charge control corresponding to the time slot  31  in the charge/discharge plan information S 3 . In this case, the charge/discharge control device  3  outputs the control signal Ct to charge the storage battery  12 . The charge/discharge device  11  that has received this control signal Ct charges the charge device  12  during the time slot B 1 . Note that the charge/discharge device  11  charges the storage battery  12  within a range of contracted electric power. 
     Here, the contracted electric power means the maximum value of the electric energy that is agreed between, for example, the consumer  10  and the electric power company and is supplied from the distribution line L 1  to the consumer  10 . The following description will be given assuming that that contracted electric power has been determined as 40 (kWh). To “charge the storage battery  12  within a range of contracted electric power” means that the charge/discharge device  11  charges the storage battery  12  in a state where the electric energy supplied from the distribution line L 1  to the consumer  10  is being kept within 40 (kWh). For example, when power consumption of the load R 1  is 30 (kWh), the charge/discharge device  11  supplies electric power at electric energy of 10 (kWh) or less to the storage battery  12 , to charge the storage battery  12 . The power consumption of the load R 1  and the electric energy of the electric power supplied to the storage battery  12  may be measured by, for example, the measuring device M 1 . In this case, the charge/discharge device  11  may charge the storage battery  12  based on the measurement result measured by the measuring device M 1 . 
     The charge/discharge control device  3  determines whether the value of the variable t is 24 or not (Step St 23 ). When the charge/discharge control device  3  determines that the value of the variable t is 24 (YES at Step St 23 ), the charge/discharge control device  3  ends the operation, considering that the control has been ended in all the time slots in the charge/discharge plan information S 3 . When the charge/discharge control device  3  determines that the value of the variable t is not 24 (NO at Step St 23 ), the charge/discharge control device  3  adds 1 to the value of the variable t (Step St 24 ), performs the operation at Step St 22 , and performs determination at Step St 23  again, considering that the control has not been ended in all the time slots in the charge/discharge plan information S 3 . 
     Note that when the value of the variable t is 9 at Step St 22 , the charge/discharge control device  3  performs the stop control corresponding to the time slot  89  in the charge/discharge plan information S 3 . In this case, the charge/discharge control device  3  outputs the control signal Ct for preventing both charging and discharging of the storage battery  12 . As described above, the charge/discharge device  11  that has received this control signal Ct, stops charge and discharge of the storage battery  12 . 
     Alternatively, when the value of the variable t is 20 at Step St 22 , the charge/discharge control device  3  performs discharge control corresponding to the time slot  320  in the charge/discharge plan information S 3 . In this case, the charge/discharge control device  3  outputs the control signal Ct to discharge the storage battery  12 . The charge/discharge device  11  that has received this control signal Ct discharges the storage battery  12  and supplies the electric power output by this discharge to the distribution line L 1 , to sell the electricity. Note that the charge/discharge device  11  discharges the storage battery  12  within a range in which an adverse current does not occur in the distribution line L 1 . 
     Here, the adverse current means a reverse power flow of the electric power supplied from downstream of the distribution line L 1  to upstream of the distribution line L 1 . When the adverse current occurs, for example, the adverse current may possibly causes a failure of the distribution transformer  101 , or the like. Thus, it is preferable that, when the consumer  10  supplies electric power to the distribution line L 1 , the electric power is supplied within the range in which the adverse current is not caused in the distribution line L 1 . For example, it is assumed that the distribution system  100  includes an ammeter M 2  that measures a current I 1  flowing through a transmission end  102  at the distribution line L 1  from the upstream to the downstream. For example, it is assumed that, while the adverse current does not occur, the value of the current I 1  is positive and while the adverse current occurs, the value of the current is negative. 
     Based on the measurement result measured by the ammeter M 2  or the like, the charge/discharge device  11  determines the maximum value of the electric energy (also referred to as a “maximum electric energy”) that can be supplied from the consumer  10  to the distribution line L 1  within the range in which the adverse current does not occur. Specifically, the charge/discharge device  11  determines the maximum electric energy based on, for example, a difference between a positive value of the current I 1 , which is indicated by the measurement result by the ammeter M 2 , and a predetermined value (e.g., 0). Note that, for example, the charge/discharge device  11  may determine a value corresponding to a product of this difference and a voltage of the distribution line L 1  as the maximum electric energy. Note that when the value of the current I 1  indicated by the measurement result by the ammeter M 2  is negative, the charge/discharge device  11  may determine the maximum electric energy as 0. Then, discharging the storage battery  12  within a range in which the adverse current does not occur in the distribution line L 1  means, for example, when the maximum electric energy is determined as 30 (kWh), the charge/discharge device  11  discharges the storage battery  12  so that the electric energy supplied from the consumer  10  to the distribution line L 1  is kept within 30 (kWh). 
     Second Embodiment 
     In a charge/discharge control device  3 B ( FIG. 1 ) according to a second embodiment, the planning unit  36  in the charge/discharge control device  3  according to the first embodiment is changed into a planning unit  36 B. A configuration other than the planning unit  36 B in the charge/discharge control device  3 B is similar to that in the charge/discharge control device  3 . 
     Planning Unit 
     Hereinafter, the planning unit according to an embodiment of the present invention will be described with reference to  FIGS. 1, 3, and 11 .  FIG. 11  is a flowchart illustrating an operation of the planning unit according to an embodiment of the present invention. 
     The charge/discharge control device  3 B (storage-battery charge/discharge device) includes the planning unit  36 B (judging device, determining device, and storage-battery charge/discharge planning device). 
     &lt;Outline&gt; 
     The planning unit  36 B, after rearranging the first price information S 1 , selects one planned electric power price and searches for the other planned electric power price meeting a predetermined condition in association with the selected one planned electric power price. The planning unit  36 B sets a charge/discharge plan based on the search result, to create the charge/discharge plan information S 3 . 
     &lt;Detail&gt; 
     The planning unit  36 B performs operations at Steps St 31  and St 32 . Note that the operations of Steps St 31  and  32  are similar to the operations of Steps St 11  and St 12 , respectively. The planning unit  36 B selects a planned electric power price from the second plan information S 2  as one planned electric power price (Step St 33 ). Note that the one planned electric power price is, for example, such a planned electric power price that the discharge control is set in the time slot associated with the one planned electric power price when the one planned electric power price meets the predetermined condition in association with the other planned electric power price. For example, the planning unit  36 B selects A 22  as the one planned electric power price. Note that, in the second price information S 2 , any of the planned electric power prices may be selected as the one planned electric power price. 
     The planning unit  36 B searches for a planned electric power price that meets the predetermined condition in association with the A 22 , which is selected as the one planned electric power price, from the second price information S 2  (Step St 34 ). The predetermined condition is the condition described at Step St 14 . The charge/discharge price ratio is a result of division performed using the other planned electric power price, which is lower one of the one and the other planned electric power prices, as a dividend and the higher one as a divisor. 
     The planning unit  363  determines whether the other planned electric power price is present or not (Step St 35 ). For example, it is assumed that the predetermined condition is met between A 1  and A 22  in the second price information S 2 , that is, for example, it is assumed that the operation result of A 1 +A 22  is smaller than the charge/discharge efficiency of the electricity storage system. In such a case, the planning unit  36 B determines that the other planned electric power price is present (YES at Step St 35 ). Then, the planning unit  36 B makes a setting such that the discharge control is to be performed in the time slot B 22 , which corresponds to A 22  serving as the one planned electric power price, and makes a setting such that the charge control is to be performed in the time slot B 1 , which corresponds to A 1  serving as the other planned electric power price. Then, the planning unit  36 B reflects these setting results in the charge/discharge plan information S 3  (Step St 36 ). 
     In the determination at Step St 35 , for example, when the planning unit  36 B determines that the other planned electric power price is absent (NO at Step St 35 ), the stop control is set in the time slot B 22 , which corresponds to A 22 , and in a time slot other than A 22 , for example, the time slot B 2 , which corresponds to A 2 . Then, the planning unit  36 B reflects these setting results in the charge/discharge plan information S 3  (Step St 37 ). 
     The planning unit  36 B determines whether settings with respect to control have been made to all the time slots in the second price information S 2  or not (Step St 38 ). When the planning unit  36 B determines that the settings with respect to control have been made to all the time slots (YES at Step St 38 ), the planning unit  36 B ends the operation. When the planning unit  36 B determines that the settings with respect to control have not been made to all the time slots (NO at Step St 38 ), the planning unit  363  performs the determination at Step St 35  again, after performing the operations of Steps St 33  and St 34 . 
     Third Embodiment 
     In a charge/discharge control device  3 C ( FIG. 1 ) according to a third embodiment, the planning unit  36  in the charge/discharge control device  3  according to the first embodiment is changed into a planning unit  36 C. A configuration other than the planning unit  36 C in the charge/discharge control device  3 C is similar to that in the charge/discharge control device  3 . 
     Planning Unit 
     Hereinafter, the planning unit according to an embodiment of the present invention will be described with reference to  FIGS. 1, 3, and 12 .  FIG. 12  is a flowchart illustrating an operation of the planning unit according to an embodiment of the present invention. 
     The charge/discharge control device  3 C (storage-battery charge/discharge device) includes the planning unit  36 C (judging device, determining device, and storage-battery charge/discharge planning device). 
     &lt;Outline&gt; 
     The planning unit  36 C, after rearranging the first price information S 1 , selects one and the other planned electric power prices. The planning unit  36 C sets charge/discharge plans in the one and the other time slots corresponding to the selected one and the other planned electric power prices, respectively. The planning unit  36 C sets the charge/discharge plan, for example, in all the time slots for 24 hours in the first price information S 1 . The planning unit  36 C creates the charge/discharge plan information S 3  in which the settings of the charge/discharge plan have been reflected. 
     &lt;Details&gt; 
     The planning unit  36 C classifies combinations of the time slots and the planned electric power prices corresponding to these time slots in the second price information S 2  into first and second groups based on the planned electric power prices (Step St 42 ). Specifically, for example, the combinations corresponding to Nos. 1 to 12 in the second price information S 2  form the first group and the combinations corresponding to Nos. 13 to 24 form the second group. 
     The planning unit  36 C selects the one planned electric power price and the other planned electric power price from the second price information S 2  (Step St 43 ). Specifically, for example, the planning unit  36 C selects the other planned electric power price from the planned electric power prices in the first group and selects the one planned electric power price from the planned electric power prices in the second group. 
     The planning unit  36 C determines (judges) whether the one and the other planned electric power prices selected at Step St 43  are to bring the economic advantage or not (Step St 44 ). Specifically, the planning unit  36 C determines whether the charge/discharge price ratio is smaller than the charge/discharge efficiency or not (Step St 44 ). Note that the charge/discharge price ratio is a result of division using the other planned electric power price, which is lower one of the one and the other planned electric power prices, as a dividend and the higher one as a divisor. 
     For example, when the planning unit  36 C determines (judges) at Step St 44  that the charge/discharge price ratio is smaller than the charge/discharge efficiency (YES at Step St 44 ), the planning unit  36 C sets the charge control to the other time slot corresponding to the other planned electric power price and sets the discharge control to the one time slot corresponding to the one planned electric power price (Step St 45 ), considering that the economic advantage for the consumer  10  is to be brought. 
     Meanwhile, for example, when the planning unit  36 C determines (judges) at Step St 44  that the charge/discharge price ratio is not smaller than the charge/discharge efficiency (NO at Step St 44 ), the planning unit  36 C sets the stop control to both the one and the other time slots corresponding to the one and the other planned electric power prices (Step St 47 ), considering that the economic advantage for the consumer  10  is not to be brought. 
     The planning unit  36 C sets control to all the time slots in the second price information S 2 , reflects these setting results in the charge/discharge plan information S 3 , and ends the operation. 
     As described above, the planning unit  36  judges the economic efficiency (economic advantage) that will be brought by charging and discharging of the storage battery  12 , for example, based on A 3  serving as the planned electric power price (first sale price) in the time slot B 3 , which is obtained by dividing a day into predetermined time periods (e.g., one hour), A 21  serving as the planned electric power price (second sale price) in the time slot B 21 , which is obtained by dividing a day into the predetermined time periods and is different from the time slot B 3 , and the charge/discharge efficiency. Based on the judgment result on this economic efficiency, the planning unit  36  determines the charge/discharge plans in the time slots B 3  and B 21  and creates the charge/discharge plan information S 3 . Accordingly, the charge/discharge plan of this storage battery  12  can be determined considering the economic efficiency that is to be brought by the charge and discharge of the storage battery  12 , based on the charge/discharge efficiency or the like. Further, controlling the charge and discharge of the storage battery  12  based on this charge/discharge plan can improve the economic advantages that are to be brought by charging and discharging of the storage battery  12 . 
     Further, at Step St 14 , the planning unit  36  determines (judges) whether, for example, the charge/discharge price ratio (A 3 /A 21 ) of A 3 , which is lower than A 21 , to A 21 , which is higher one of A 3  and A 21  serving as the planned electric power prices, is smaller than the charge/discharge efficiency or not. For example, when the planning unit  36  determines that the charge/discharge price ratio (A 3 /A 21 ) is smaller than the charge/discharge efficiency, the planning unit  36  determines the charge/discharge plan such that charge is performed in the time slot B 3 , which corresponds to A 3 , and discharge is performed in the time slot  321 , which corresponds to A 21 , among A 3  and A 21 , to create the charge/discharge plan information S 3 . Thus, the time slot during which the storage battery  12  is charged and the time slot during which the storage battery  12  is discharged are determined in a pair. That is, the charge/discharge plan can be determined such that both charge and discharge of the storage battery  12  are reliably performed, considering the economic efficiency of the storage battery  12 . 
     Alternatively, for example, when the planning unit  36  determines (judges) that the charge/discharge price ratio (A 3 /A 21 ) is not smaller than the charge/discharge efficiency, the planning unit  36  determines the charge/discharge plan such that neither charge nor discharge of the storage battery  12  is performed in A 3  and A 21 , to create the charge/discharge plan information S 3 . Thus, when the planning unit  36  judges that the economic advantage is not to be provided, the planning unit  36  can determine the charge/discharge plan such that the storage battery  12  is neither charged nor discharged. Thus, for example, charging and discharging of the storage battery  12  that are not to bring economic advantage can be prevented. 
     Further, the measuring device M 1  receives the first price information S 1 . In the first price information S 1 , set are the planned electric power prices A 1  to A 24  corresponding to the plurality of time slots B 1  to B 24 , which are obtained by dividing a day into the predetermined time periods (e.g., one hour). The planning unit  36  creates the charge/discharge plan information S 3  based on the charge/discharge price ratio. The charge/discharge price ratio is calculated using A 21  which is the highest price and A 3  which is the lowest price among A 1  to A 24  serving as the plurality of planned electric power prices in the first price information S 1  received by the measuring instrument M 1 . Thus, the charge/discharge plan can be determined such that the storage battery  12  is charged/discharged in a time slot during which the greatest economic advantage is expected in the first price information S 1 . 
     Further, the measuring device Ni receives the first price information S 1 . The planning unit  36 C (third embodiment) classifies the combinations in the second price information S 2  into the first group and the second group based on the planned electric power prices in the second price information S 2 , which is based on the first price information S 1  received by the measuring device M 1 . Note that the combinations in the second price information S 2  indicate combinations of the time slots in the second price information S 2  and the planned electric power prices corresponding to these time slots. The planning unit  36 C selects the other planned electric power price from the planned electric power prices in the first group, and selects the one planned electric power price from the planned electric power prices in the second group. Thereafter, the planning unit  36 C creates the charge/discharge plan information S 3 , based on the charge/discharge price ratio calculated using the one and the other planned electric power prices. Thus, the difference can be generated between the one and the other planned electric power prices, depending on how the combinations in the second price information S 2  are classified into the first group and the second group. Thus, the charge/discharge plan can be determined such that the economic advantage is increased by virtue of charging and discharging of the storage battery  12 . 
     Further, the charge/discharge efficiency is determined based on the product of the charge efficiency p when electric power is charged to the storage battery  12  and the discharge efficiency q when the electric power charged to the storage battery  12  is discharged. Thus, the charge/discharge plan of the storage battery  12  can be determined in consideration of the economic efficiency in which both the charge efficiency p and the discharge efficiency q have been reflected. 
     Further, the charge/discharge control device  3  includes the planning unit  36  and the control unit  37 . The planning unit  36  creates the charge/discharge plan information S 3 . The control unit  37  controls charge and discharge of the storage battery  12  based on the charge/discharge plan information S 3  created by the planning unit  36 . The charge/discharge control device  3  can control charge and discharge of the storage battery  12  considering the economic efficiency based on the charge/discharge efficiency and the like. 
     Note that the first to third embodiments are simply for facilitating the understanding of the present invention and are not in any way to be construed as limiting the present invention. The present invention may variously be modified or altered without departing from the scope and encompass equivalents thereof. 
     The first embodiment describes that the first price information S 1  indicates the planned electric power prices in every one hour; however, it is note limited thereto. For example, the first price information S 1  may indicate the planned electric power prices in every 30 minutes or the like. In the case where the first price information S 1  indicates the planned electric power prices in every 30 minutes, the value of the variable K is from 1 to 24. 
     Further, the first embodiment describes that the charge/discharge device  11  determines the maximum electric energy of the electric power supplied from the consumer  10  to the distribution line L 1  in the range in which the adverse current does not occur; however, it is not limited thereto. For example, the maximum electric energy that can be supplied from the consumer  10  to the distribution line L 1  may be predetermined in the range in which the adverse current is not caused, based on a power flow calculation in the distribution system  100  or the like. 
     Further, the first embodiment describes that, in the first price information S 1 , the prices of the electric power for sale is the same as the prices of the electric power for purchase; however, it is not limited thereto. For example, the price of the electric power for sale and the price of the electric power for purchase in the same time slot may be different from each other. In this case, a configuration may be such that, when the discharge control is performed at Step St 22 , the charge/discharge control device  3  determines whether the economic advantage will be brought by discharge or not, based on the charged amount of the storage battery  12  and the power consumption of the load R 1 , and when the charge/discharge control device  3  determines that the economic advantage will be brought, the charge/discharge control device  3  outputs the control signal Ct for discharging the storage battery  12 . Note that, for example, a configuration may be such that, when the price of the electric power for sale is higher than the price of the electric power for purchase and the electric energy larger than the power consumption of the load R 1  can be discharged from the storage battery  12 , the charge/discharge control device  3  determines that the economic advantage will be provided. For example, a configuration may be such that, when the price of the electric power for sale is lower than the price of the electric power for purchase, the charge/discharge control device  3  determines that the economic advantage will not be provided. 
     Further, a configuration may be made such that, when discharge control is performed at Step St 22 , the electric power output from the storage battery  12  is supplied to the load R 1  and the charge/discharge device  11  discharges the storage battery  12  within a range in which an adverse current from the consumer  10  to the distribution line L 1  does not occur. In this case, the electric energy of the electric power for purchase can be reduced, resulting in the economic advantage being brought to the consumer  10 . 
     Further, the second embodiment may omit the rearrangement at Step St 32  ( FIG. 11 ). In this case, at Steps St 33  and St 34 , the operations are performed based on the first price information S 1 . 
     Further, the second embodiment describes that, after the one planned electric power price is selected at Step St 33 , the other planned electric power price is searched at Step St 34 ; however, it is not limited thereto. For example, a configuration may be such that, after the other planned electric power price is selected at Step St 33 , the one planned electric power price is searched at Step St 34 . 
     Further, the third embodiment describes that the other planned electric power price is, selected from the planned electric power prices in the first group and the one planned electric power price is selected from the planned electric power prices in the second group at Step St 43 ; however, it is not limited thereto. For example, a configuration may be such that, regardless of the first or the second group, the planning unit  36 C selects two planned electric power prices different from each other in the second price information S 2  as the one and the other planned electric power prices. In this case, since the difference generated between the two planned electric power prices, it is possible to determine the charge/discharge plan of the storage battery  12  such that the economic advantage when the storage battery  12  is charged/discharged is to be increased. 
     REFERENCE SIGNS LIST 
     
         
           3 ,  3 B,  3 C charge/discharge control device 
           12  storage battery 
           36 ,  36 B,  36 C planning unit 
           37  control unit