Patent Publication Number: US-2021170903-A1

Title: Power management system and server

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This nonprovisional application claims priority to Japanese Patent Application No. 2019-222036 filed with the Japan Patent Office on Dec. 9, 2019, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     Field 
     The present disclosure relates to a power management system and a server, and more specifically to a technique for regulation of supply and demand of electric power by using a power storage. 
     Description of the Background Art 
     A technique for regulation of supply and demand of electric power by using a mobile body such as an electric vehicle has been known. For example, Japanese Patent Laying-Open No. 2012-048286 discloses a power management system including a plurality of electric vehicles each including a power storage and a charge monitoring control center. The charge monitoring control center invites an electric vehicle of which power storage is to be charged, determines a charging location and an amount of charging of each electric vehicle that has accepted the invitation, and instructs each electric vehicle to move to the charging location. 
     SUMMARY 
     In the power management system described in Japanese Patent Laying-Open No. 2012-048286, a user of an electric vehicle can be given an incentive by carrying out charging in response to a request from the charge monitoring control center. All users, however, do not place highest priority on the incentive. Some users desire suppression of deterioration of the power storage rather than reception of the incentive for meeting the request from the charge monitoring control center. The power management system described in Japanese Patent Laying-Open No. 2012-048286 does not pay attention to such users and there is a room for improvement. 
     The present disclosure was made to solve the problem above, and an object thereof is to provide a power management system and a server that can request a user of a power storage to regulate supply and demand of electric power with attention being paid to a user who desires suppression of deterioration of the power storage. 
     A power management system according to the present disclosure includes a plurality of power storages and a server. Each of the plurality of power storages carries out at least one of external charging and external power feed. External charging is charging of the power storage with electric power supplied from the outside. External power feed is supply of electric power from the power storage to the outside. The server includes a selector, a scheduler, and a request processor. The selector selects at least one of the plurality of power storages. The scheduler makes a schedule for the selected power storage. The request processor requests a user of the selected power storage to control at least one of external charging and external power feed in accordance with the made schedule. The server obtains for each power storage, desire information that indicates at least one of a first desire level and a second desire level, the first desire level indicating a level of the user&#39;s desire for suppression of deterioration of the power storage, the second desire level indicating a level of the user&#39;s desire for acquisition of an incentive for meeting the request, and carries out at least one of selection of the power storage and making of the schedule based on the obtained desire information. 
     A server according to the present disclosure is included in a power management system including a plurality of power storages. Each of the plurality of power storages carries out at least one of external charging and external power feed. External charging is charging of the power storage with electric power supplied from the outside. External power feed is supply of electric power from the power storage to the outside. The server includes a selector, a scheduler, and a request processor. The selector selects at least one of the plurality of power storages. The scheduler makes a schedule for the selected power storage. The request processor requests a user of the selected power storage to control at least one of external charging and external power feed in accordance with the made schedule. The server obtains for each power storage, desire information that indicates at least one of a first desire level and a second desire level, the first desire level indicating a level of user&#39;s desire for suppression of deterioration of the power storage, the second desire level indicating a level of user&#39;s desire for acquisition of an incentive for meeting the request, and carries out at least one of selection of the power storage and making of the schedule based on the obtained desire information. 
     The request processor of the server can request the user of the power storage to regulate supply and demand of electric power. The request processor may transmit a signal to a communication apparatus registered in the server in association with the user of the power storage. The user of each of the plurality of power storages can contribute to regulation of supply and demand of electric power by controlling at least one of external charging and external power feed by the power storage in accordance with the request from the request processor (or by permitting remote control of the power storage by the server during a period indicated in the schedule). A user who prefers suppression of deterioration of the power storage to acquisition of the incentive in the desire information is also referred to as a “first user” below. A user who prefers acquisition of the incentive to suppression of deterioration of the power storage in the desire information is also referred to as a “second user.” 
     The server carries out at least one of selection of the power storage and making of the schedule based on the desire information. For example, for a request which may cause deterioration of the power storage, in selection of a power storage, the server may make the power storage of the first user less likely to be selected. In making a schedule for the power storage of the first user, the server may make a schedule in which the power storage is less likely to deteriorate. The server can thus adjust susceptibility of each power storage to deterioration based on at least one of selection of the power storage and making of the schedule. Therefore, according to the server, when a request for regulation of supply and demand of electric power is issued to a user of the power storage, the request can be issued with attention being paid to the user who desires suppression of deterioration of the power storage. 
     The desire information may be at least one of information that indicates the level of the user&#39;s desire for suppression of deterioration of the power storage by any of desiring and not desiring suppression of deterioration of the power storage and information that indicates the level of the user&#39;s desire for acquisition of the incentive by any of desiring and not desiring acquisition of the incentive. 
     According to the configuration, users of the power storages can be categorized into the first user (that is, the user who prefers suppression of deterioration of the power storage to acquisition of the incentive) and the second user (that is, the user who prefers acquisition of the incentive to suppression of deterioration of the power storage). The server can issue a request suitable for each user by carrying out at least one of selection of the power storage and making of the schedule in manners different between the first user and the second user. 
     Though description is given above assuming that the desire information indicates each of the first desire level and the second desire level in two levels (desiring and not desiring) with the users of the power storages being categorized into the first user and the second user, the desire information is not limited to information that indicates each of the first desire level and the second desire level in two levels. The desire information may be information that indicates each desire level in three or more levels or information that indicates each desire level in continuous values from 0 to 100. 
     When the selector selects a power storage of which a user is requested to carry out external charging by the request processor, the selector may preferentially sequentially select the power storage lower in first desire level or the power storage higher in second desire level. 
     Deterioration of the power storage tends to proceed more as a frequency of charging is higher. According to the configuration, when the selector selects the power storage of which the user is requested to carry out external charging, the power storage of the user lower in first desire level or higher in second desire level is preferentially sequentially selected. As the power storage of the user lower in first desire level is preferentially sequentially selected, increase in frequency of charging of the power storage of the user higher in first desire level can be suppressed. As increase in frequency of charging of the power storage is suppressed, deterioration of the power storage is suppressed. As the power storage of the user higher in second desire level is preferentially sequentially selected, the user higher in second desire level is more likely to acquire the incentive. 
     When the selector selects a power storage of which a user is requested to carry out external power feed by the request processor, the selector may preferentially sequentially select the power storage higher in first desire level or the power storage higher in second desire level. 
     The power storage tends to deteriorate as it is left stand in a high SOC state. The state of charge (SOC) represents a remaining amount of stored power, and it is expressed, for example, as a ratio of a current amount of stored power to an amount of stored power in a fully charged state that ranges from 0 to 100%. According to the configuration, when the selector selects a power storage of which the user is requested to carry out external power feed, the power storage of the user higher in first desire level or higher in second desire level is preferentially sequentially selected. As the power storage of the user higher in first desire level is preferentially sequentially selected, the SOC of the power storage of the user higher in first desire level can be lowered. By lowering the SOC of the power storage, deterioration of the power storage is suppressed. As the power storage of the user higher in second desire level is preferentially sequentially selected, the user higher in second desire level is more likely to acquire the incentive. 
     When the selector selects a power storage of which a user is requested to carry out external power feed by the request processor, the selector may preferentially sequentially select the power storage higher in first desire level or the power storage lower in second desire level from among power storages that satisfy a prescribed condition. 
     According to the configuration, when the selector selects a power storage of which a user is requested to carry out external power feed, only the power storage that satisfies the prescribed condition is selected. The prescribed condition may be satisfied when the SOC of the power storage is equal to or larger than a prescribed value or when a temperature of the power storage is equal to or larger than a prescribed value. When the selector selects a power storage of which a user is requested to carry out external power feed, the power storage of the user higher in first desire level or lower in second desire level is preferentially sequentially selected. Therefore, the power storage of the user higher in first desire level or lower in second desire level being left stand in a state susceptible to deterioration (for example, in a high SOC state) can be suppressed. When a temperature of the power storage is high, an abnormal condition may be occurring in the power storage. By lowering the SOC of the power storage at a high temperature, safety can be enhanced. 
     According to the configuration, when the selector selects a power storage of which a user is requested to carry out external power feed, the power storage of the user higher in first desire level (or lower in second desire level) is more likely to be selected. Deterioration of the power storage of the user higher in first desire level (or lower in second desire level) can thus be suppressed. By preferentially selecting the power storage of the user higher in first desire level (or lower in second desire level) in selection of the power storage, however, an opportunity for the user lower in first desire level (or higher in second desire level) to acquire the incentive may be lost. In view of such a problem, a configuration below may be adopted. 
     The server may manage for each user, a unit price of the incentive to be given to the user that meets the request from the request processor, and increase the unit price of the incentive for the user lower in first desire level or the user higher in second desire level. 
     According to the configuration, the unit price of the incentive is increased for a user lower in first desire level or higher in second desire level. By lowering the first desire level (or raising the second desire level), the user of the power storage is more likely to obtain a high incentive at the sacrifice of susceptibility of the power storage to deterioration. Fairness among users can thus be ensured. 
     The plurality of power storages may be mounted on a plurality of mobile bodies, respectively. The server may obtain next departure time for each mobile body. Each of the plurality of mobile bodies may move with electric power stored in the power storage. When the scheduler makes a charging schedule for a selected mobile body, the scheduler may make the charging schedule to make a time lag between charging end time and the next departure time smaller in a mobile body of the user higher in first desire level or the user lower in second desire level. 
     It is expected that, when the mobile body carries out external charging, the SOC of the power storage becomes higher and the power storage will be in the high SOC state at the charging end time. It is expected that, as the mobile body departs (that is, moves), electric power in the power storage is consumed and the SOC of the power storage is lowered. Therefore, as a time lag between the charging end time and the next departure time is smaller, a time period for which the power storage is left stand in the high SOC state is expected to be shorter. According to the configuration, the charging schedule is made such that the mobile body of the user higher in first desire level or lower in second desire level is smaller in time lag between the charging end time and the next departure time. The power storage of the user higher in first desire level or lower in second desire level being left stand in the high SOC state (and deterioration of the power storage) can thus be suppressed. 
     The server may predict the next departure time for each mobile body based on history data (for example, a time period of stay from arrival at a charging location until departure) of each mobile body. The server may obtain the next departure time (that is, a user&#39;s schedule) from the user of the mobile body. The user can transmit the next departure time to the server through any communication equipment (for example, a portable terminal). 
     The selector may set an upper limit value of the number of times of charging per unit period for each power storage based on the desire information, and exclude a power storage of which the number of times of charging per unit period has exceeded the upper limit value from candidates for selection. 
     Deterioration of the power storage tends to proceed more as the number of times of charging per unit period is larger. The server can exclude the power storage of which the number of times of charging per unit period has exceeded the upper limit value from candidates for selection. Progress of deterioration of the power storage by external charging or external power feed in response to the request from the request processor can thus be suppressed. Since the server sets the upper limit value of the number of times of charging per unit period based on the desire information, deterioration of the power storage of the user higher in first desire level or lower in second desire level can be suppressed. 
     A process from start of charging until stop of charging is counted as one charging. Transition of the power storage from a non-charging state (that is, a state in which charging is not being carried out) to a charging state (that is, a state in which charging is being carried out) is defined as start of charging. Transition of the power storage from the charging state to the non-charging state is defined as stop of charging. Transition of the power storage from the charging state to a discharging state (that is, a state in which discharging is being carried out) is also encompassed in stop of charging. 
     Setting of the upper limit value includes not only setting of an effective numeric value as the upper limit value but also setting of “no upper limit value.” The selector may substantially set “no upper limit value” by setting a “MAX value (or infinity)” as the upper limit value. 
     Any power management system described above may further include a plurality of portable terminals carried by respective users of the plurality of power storages. Each of the plurality of portable terminals may accept input from the user of the power storage, and when the desire information is input by the user of the power storage, each of the plurality of portable terminals may transmit the input desire information to the server. 
     According to the configuration, the user can transmit the desire information to the server through the portable terminal. 
     In any power management system described above, the plurality of power storages may be mounted on a plurality of mobile bodies, respectively. Any power management system described above may further include a plurality of user terminals mounted on the plurality of mobile bodies, respectively. Each of the plurality of user terminals may accept input from the user of the power storage, and when the user of the power storage inputs the desire information, each of the plurality of user terminals may transmit the input desire information to the server. 
     According to the configuration, the user can transmit the desire information to the server through the user terminal of the mobile body. 
     An input from the user may be an input to a graphical user interface (GUI) or an audio input. The user may provide the input by operating a member such as a button or a lever. A signal from the portable terminal or the user terminal to the server may directly be transmitted from the portable terminal or the user terminal to the server, or from the portable terminal or the user terminal to the server via another apparatus. 
     In any power management system described above, the plurality of power storages may be mounted on a plurality of vehicles, respectively. Any power management system described above may further include a plurality of power facilities electrically connectable to the plurality of vehicles and a power grid that supplies electric power to each of the plurality of power facilities. The request processor may transmit a signal that requests a user of the vehicle to control at least one of external charging and external power feed in accordance with the schedule, to at least one of communication equipment mounted on the vehicle and a portable terminal carried by the user of the vehicle. 
     According to the configuration, as the server transmits the signal to the vehicle (more specifically, communication equipment) and/or the portable terminal, balance of supply and demand of the power grid can be regulated. 
     The signal from the server to the vehicle or the portable terminal may directly be transmitted from the server to the vehicle or the portable terminal or from the server to the vehicle or the portable terminal via another apparatus (for example, the power facility). 
     The mobile body may be an electrically powered vehicle. The electrically powered vehicle refers to a vehicle that travels with electric power stored in a power storage mounted on the vehicle. The mobile body may remotely be controllable or may be self-driving. The mobile body may be a flying object (for example, a drone). 
     The foregoing and other objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of the present disclosure when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing a configuration of a vehicle included in a power management system according to an embodiment of the present disclosure. 
         FIG. 2  is a diagram showing a schematic configuration of a power management system according to the embodiment of the present disclosure. 
         FIG. 3  is a diagram showing a power grid, a plurality of pieces of EVSE, and a plurality of vehicles included in the power management system according to the embodiment of the present disclosure. 
         FIG. 4  is a diagram showing a detailed configuration of a vehicle controller, a server, and a portable terminal included in the power management system according to the embodiment of the present disclosure. 
         FIG. 5  is a diagram for illustrating details of vehicle information and user information held by the server shown in  FIG. 4 . 
         FIG. 6  is a flowchart showing processing performed by the server when an aggregator trades electric power in a power market in the power management system according to the embodiment of the present disclosure. 
         FIG. 7  is a flowchart showing details of processing involved with selection of a DR vehicle shown in  FIG. 6 . 
         FIG. 8  is a diagram showing an exemplary charging schedule in which the number of times of charging is set to one. 
         FIG. 9  is a diagram showing an exemplary charging schedule in which the number of times of charging is set to five. 
         FIG. 10  is a diagram for illustrating selection of a DR vehicle made in the processing shown in  FIG. 7 . 
         FIG. 11  is a diagram for illustrating making of a charging schedule in the processing shown in  FIG. 6 . 
         FIG. 12  is a flowchart showing charging and discharging control of a power storage of a DR vehicle in the power management system according to the embodiment of the present disclosure. 
         FIG. 13  is a flowchart showing charging and discharging control of a power storage of a non-DR vehicle in the power management system according to the embodiment of the present disclosure. 
         FIG. 14  is a diagram for illustrating a modification of selection of a DR vehicle shown in  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of the present disclosure will be described below in detail with reference to the drawings. The same or corresponding elements in the drawings have the same reference characters allotted and description thereof will not be repeated. 
     A power management system according to this embodiment includes a plurality of vehicles. Though the plurality of vehicles in the power management system may be different from one another in configuration, they are identical in configuration in this embodiment. Each of a plurality of vehicles included in the power management system is denoted as a “vehicle  50 ” below and each of a plurality of pieces of EVSE included in the power management system is denoted as “EVSE  40 ” below, unless they are described as being distinguished from one another. EVSE means electric vehicle supply equipment. 
       FIG. 1  is a diagram showing a configuration of vehicle  50  included in the power management system according to this embodiment. Referring to  FIG. 1 , vehicle  50  includes a battery  130  that stores electric power for traveling. Battery  130  includes a secondary battery such as a lithium ion battery or a nickel metal hydride battery. In this embodiment, a battery assembly including a plurality of lithium ion batteries is adopted as the secondary battery. The battery assembly is composed of a plurality of cells electrically connected to one another. Instead of the secondary battery, another power storage such as an electric double layer capacitor may be adopted. Battery  130  according to this embodiment corresponds to an exemplary “power storage” according to the present disclosure. 
     Vehicle  50  includes an electronic control unit (which is referred to as an “ECU” below)  150 . ECU  150  carries out charging control and discharging control of battery  130 . ECU  150  controls communication with the outside of vehicle  50 . Vehicle  50  further includes a monitoring module  131  that monitors a state of battery  130 . Monitoring module  131  includes various sensors that detect a state (for example, a voltage, a current, and a temperature) of battery  130  and outputs a result of detection to ECU  150 . ECU  150  can obtain a state (for example, a temperature, a current, a voltage, an SOC, and an internal resistance) of battery  130  based on an output (that is, detection values from various sensors) from monitoring module  131 . Vehicle  50  may be an electric vehicle (EV) that can travel only with electric power stored in battery  130  or a plug-in hybrid vehicle (PHV) that can travel with both of electric power stored in battery  130  and output from an engine (not shown). Though vehicle  50  is driven by a user in this embodiment, vehicle  50  may be self-driving. 
     Vehicle  50  includes an inlet  110  and a charger-discharger  120  adapted to a power feed type of EVSE  40 . Inlet  110  receives electric power supplied from the outside of vehicle  50 . Inlet  110  outputs electric power supplied from charger-discharger  120  to the outside of vehicle  50 . Though  FIG. 1  shows only inlet  110  and charger-discharger  120 , vehicle  50  may include an inlet and a charger-discharger for each power feed type so as to adapt to a plurality of power feed types (for example, an alternating-current (AC) type and a direct-current (DC) type). 
     A charging cable  42  is connected to EVSE  40 . Charging cable  42  may always be connected to EVSE  40  or may be attachable to and removable from EVSE  40 . Charging cable  42  includes a connector  43  at its tip end and contains a power line. Connector  43  of charging cable  42  can be connected to inlet  110 . As connector  43  of charging cable  42  connected to EVSE  40  is connected to inlet  110  of vehicle  50 , EVSE  40  and vehicle  50  are electrically connected to each other. Electric power can thus be supplied from EVSE  40  through charging cable  42  to vehicle  50 . 
     Charger-discharger  120  is located between inlet  110  and battery  130 . Charger-discharger  120  includes a relay that switches between connection and disconnection of an electric power path from inlet  110  to battery  130  and a power conversion circuit (neither of which is shown). For example, a bidirectional converter can be adopted as the power conversion circuit. Each of the relay and the power conversion circuit included in charger-discharger  120  is controlled by ECU  150 . Vehicle  50  further includes a monitoring module  121  that monitors a state of charger-discharger  120 . Monitoring module  121  includes various sensors that detect a state (for example, a voltage, a current, and a temperature) of charger-discharger  120  and outputs a result of detection to ECU  150 . In this embodiment, monitoring module  121  detects a voltage and a current input to and output from the power conversion circuit. 
     As EVSE  40  outside vehicle  50  and inlet  110  are connected to each other through charging cable  42 , electric power can be supplied and received between EVSE  40  and vehicle  50 . Therefore, external charging by vehicle  50  can be carried out (that is, electric power can be supplied from the outside of vehicle  50  to charge battery  130  of vehicle  50 ). Electric power for external charging is supplied, for example, from EVSE  40  through charging cable  42  to inlet  110 . Charger-discharger  120  converts electric power received at inlet  110  into electric power suitable for charging of battery  130  and outputs resultant electric power to battery  130 . As EVSE  40  and inlet  110  are connected to each other through charging cable  42 , external power feed by vehicle  50  (that is, power feed from vehicle  50  through charging cable  42  to EVSE  40 ) can be carried out. Electric power for external power feed is supplied from battery  130  to charger-discharger  120 . Charger-discharger  120  converts electric power supplied from battery  130  into electric power suitable for external power feed and outputs resultant electric power to inlet  110 . When any of external charging and external power feed is performed, the relay of charger-discharger  120  is closed (connected), and when neither of external charging and external power feed is performed, the relay of charger-discharger  120  is opened (disconnected). 
     The configuration of charger-discharger  120  is not limited as above and can be modified as appropriate. Charger-discharger  120  may include, for example, at least one of a rectification circuit, a power factor correction (PFC) circuit, an insulating circuit (for example, an insulating transformer), an inverter, and a filter circuit. When vehicle  50  carries out external power feed to AC type EVSE, charger-discharger  120  may subject electric power discharged from battery  130  to DC/AC conversion and resultant AC power may be supplied from vehicle  50  to the EVSE. When vehicle  50  carries out external power feed to DC type EVSE, vehicle  50  may supply DC power to the EVSE and an inverter contained in the EVSE may carry out DC/AC conversion. Standards of the DC type EVSE may be any of CHAdeMO, Combined Charging System (CCS), GB/T, and Tesla. 
     ECU  150  includes a processor  151 , a random access memory (RAM)  152 , a storage  153 , and a timer  154 . For example, a central processing unit (CPU) can be adopted as processor  151 . RAM  152  functions as a work memory that temporarily stores data to be processed by processor  151 . Storage  153  can store information that is put thereinto. Storage  153  includes, for example, a read only memory (ROM) and a rewritable non-volatile memory. Storage  153  stores not only a program but also information (for example, a map, a mathematical expression, and various parameters) to be used by a program. As a program stored in storage  153  is executed by processor  151 , various types of control by ECU  150  are carried out in this embodiment. Various types of control by ECU  150  are not limited to control carried out by software but can also be carried out by dedicated hardware (electronic circuitry). Any number of processors may be provided in ECU  150  and a processor may be prepared for each prescribed type of control. 
     Timer  154  notifies processor  151  that the set time has come. As the time set in timer  154  comes, timer  154  transmits a signal to that effect to processor  151 . In this embodiment, a timer circuit is adopted as timer  154 . Timer  154  may be implemented by software instead of hardware (timer circuitry). ECU  150  can obtain current time from a real time clock (RTC) circuit (not shown) contained in ECU  150 . 
     Vehicle  50  further includes a travel driving unit  140 , an input apparatus  160 , a notification apparatus  170 , communication equipment  180 , and a drive wheel W. Vehicle  50  is not limited to a front-wheel-drive vehicle shown in  FIG. 1  and it may be a rear-wheel-drive vehicle or a four-wheel-drive vehicle. 
     Travel driving unit  140  includes a not-shown power control unit (PCU) and a motor generator (MG), and allows vehicle  50  to travel with electric power stored in battery  130 . The PCU includes, for example, a controller including a processor, an inverter, a converter, and a relay (none of which is shown). The relay included in the PCU is referred to as a “system main relay (SMR)” below. The controller of the PCU receives an instruction (a control signal) from ECU  150  and controls the inverter, the converter, and the SMR of the PCU in accordance with the instruction. The MG is implemented, for example, by a three-phase AC motor generator. The MG is driven by the PCU and rotates drive wheel W. The MG performs regeneration and supplies regenerated electric power to battery  130 . The SMR switches between connection and disconnection of an electric power path from battery  130  to the PCU. The SMR is closed (connected) when vehicle  50  travels. 
     Input apparatus  160  accepts an input from a user. Input apparatus  160  is operated by a user and outputs a signal corresponding to the operation by the user to ECU  150 . Communication may be wired or wireless. Examples of input apparatus  160  include various switches, various pointing devices, a keyboard, and a touch panel. An operation portion of a car navigation system may be adopted as input apparatus  160 . A smart speaker that accepts audio input may be adopted as input apparatus  160 . 
     Notification apparatus  170  performs prescribed processing for giving a notification to a user (for example, a driver and/or a passenger of vehicle  50 ) when a request is given from ECU  150 . Notification apparatus  170  may include at least one of a display apparatus (for example, a touch panel display), a speaker (for example, a smart speaker), and a lamp (for example, a malfunction indicator lamp (MIL)). Notification apparatus  170  may be implemented by a meter panel, a head-up display, or a car navigation system. 
     Communication equipment  180  includes various communication interfaces (UF). Communication equipment  180  may include a data communication module (DCM). ECU  150  wirelessly communicates with a communication apparatus outside vehicle  50  through communication equipment  180 . 
     Though not shown, vehicle  50  includes various sensors (for example, a position sensor, an outside air temperature sensor, a vehicle speed sensor, and an odometer) that detect a state of vehicle  50  in real time. The state of vehicle  50  is successively detected and recorded in storage  153  of ECU  150 . The position sensor may be a sensor based on the global positioning system (GPS). The position sensor may be contained in a car navigation system (not shown) mounted on vehicle  50 . 
     An electric power system dependent on a large-scale power plant (an intensive energy resource) possessed by an electric power utility company has recently been reviewed and a scheme for utilizing an energy resource possessed by each demand side (which is also referred to as “demand side resources (DSR)” below) in the electric power system has been constructed. The DSR functions as distributed energy resources (which are also referred to as “DER” below). 
     A virtual power plant (VPP) has been proposed as a scheme for utilizing the DSR for an electric power system. The VPP refers to a scheme in which a large number of DER (for example, DSR) are put together according to a sophisticated energy management technology that makes use of the Internet of Things (IoT) and the DER are remotely controlled as being integrated as if the DER functioned as a single power plant. In the VPP, an electric utility that puts the DER together to provide an energy management service is referred to as an “aggregator.” An electric power utility company, for example, in coordination with an aggregator, can balance between supply and demand of electric power based on demand response (which is also referred to as “DR” below). 
     DR is an approach to balancing between supply and demand of electric power by issuing a prescribed request to each demand side by using a demand response signal (which is also referred to as a “DR signal” below). The DR signal is broadly categorized into two types of a DR signal that requests suppression of power demand or backfeeding (which is also referred to as a “DR suppression signal” below) and a DR signal that requests increase in power demand (which is also referred to as a “DR increase signal” below). 
     A vehicle grid integration (VGI) system is adopted as the power management system according to this embodiment. In the VGI system, an electrically powered vehicle (that is, vehicle  50  described above) including a power storage is adopted as DSR for realizing VPP. 
       FIG. 2  is a diagram showing a schematic configuration of the power management system according to this embodiment. A VGI system  1  shown in  FIG. 2  corresponds to an exemplary “power management system” according to the present disclosure. Though  FIG. 2  shows only one of each of the vehicle, the EVSE, and an aggregator server, VGI system  1  includes a plurality of vehicles, a plurality of pieces of EVSE, and a plurality of aggregator servers. Any independent number of vehicles, pieces of EVSE, and aggregator servers may be included in VGI system  1 , and the number may be set to ten or more or one hundred or more. Each vehicle included in VGI system  1  may be a personally owned vehicle (POV) or a MaaS (mobility as a service) vehicle. The MaaS vehicle refers to a vehicle managed by a MaaS entity. Though  FIG. 2  shows only a single portable terminal, the portable terminal is carried by each user of the vehicle. Though  FIG. 2  illustrates home EVSE, VGI system  1  may include public EVSE that can be used by a large number of unspecified users. 
     Referring to  FIG. 2 , VGI system  1  includes a power transmission and distribution utility server  10  (which is also simply referred to as a “server  10 ” below), a smart meter  11 , an aggregator server  30  (which is also simply referred to as a “server  30 ” below), EVSE  40 , vehicle  50  (see  FIG. 1 ), a home energy management system-gateway (HEMS-GW)  60 , a data center  70 , a portable terminal  80 , and a power grid PG. In this embodiment, a smartphone equipped with a touch panel display is adopted as portable terminal  80 . Without being limited thereto, any portable terminal can be adopted as portable terminal  80 , and a tablet terminal, a wearable device (for example, a smart watch), an electronic key, or a service tool can also be adopted. 
     Server  10  belongs to a power transmission and distribution utility. In this embodiment, an electric power utility company serves also as a power generation utility and a power transmission and distribution utility. The electric power utility company constructs a power network (that is, power grid PG) with a power plant and a power transmission and distribution facility which are not shown, and maintains and manages server  10 , smart meter  11 , EVSE  40 , HEMS-GW  60 , and power grid PG. Power grid PG according to this embodiment corresponds to an exemplary “power grid” according to the present disclosure. In this embodiment, the electric power utility company corresponds to a system operator that operates power grid PG. 
     The electric power utility company can make a profit, for example, by dealing with a demand side (for example, an individual or a company) that uses electric power. The electric power utility company provides each demand side with a smart meter. For example, a user of vehicle  50  shown in  FIG. 2  is provided with smart meter  11 . A meter ID (identification information for identification of each smart meter) is provided for each smart meter, and server  10  manages a value of measurement by each smart meter as being distinguished based on the meter ID. The electric power utility company can know an amount of power usage for each demand side based on a value of measurement by each smart meter. 
     In VGI system  1 , an ID (identification information) for identification among a plurality of aggregators is provided for each aggregator. Server  10  manages information for each aggregator as being distinguished based on the ID of the aggregator. The aggregator provides an energy management service by putting together amounts of electric power controlled by demand sides under the control thereof. The aggregator can control the amount of electric power by requesting each demand side to level electric power by using a DR signal. 
     Server  30  belongs to an aggregator. Server  30  includes a controller  31 , a storage  32 , and a communication apparatus  33 . Controller  31  includes a processor, performs prescribed information processing, and controls communication apparatus  33 . Details of the configuration of server  30  will be described later. In VGI system  1 , an electrically powered vehicle (for example, a POV or a MaaS vehicle) is adopted as DSR managed by the aggregator (and server  30 ). A demand side can control an amount of electric power by means of the electrically powered vehicle. The aggregator may procure capacity (capability of supply of electricity) not only from vehicle  50  but also from a resource other than vehicle  50  (for example, a vending machine, a plant factory, or biomass). The aggregator can make a profit, for example, by dealing with an electric power utility company. The aggregator may be divided into an upper aggregator that contacts a power transmission and distribution utility (for example, the electric power utility company) and a lower aggregator that contacts a demand side. 
     Data center  70  includes a controller  71 , a storage  72 , and a communication apparatus  73 . Controller  71  includes a processor, performs prescribed information processing, and controls communication apparatus  73 . Storage  72  can store various types of information. Communication apparatus  73  includes various types of communication I/Fs. Controller  71  communicates with the outside through communication apparatus  73 . Data center  70  manages information on a plurality of registered portable terminals (including portable terminals  80 ). Information on the portable terminal includes not only information on the terminal itself but also information on a user who carries the portable terminal. Examples of the information on the terminal itself include a communication address of the portable terminal. Examples of the information on the user include a vehicle ID of vehicle  50  belonging to the user. A terminal ID (identification information for identification of the portable terminal) is provided for each portable terminal and data center  70  manages information for each portable terminal as being distinguished based on the terminal ID. The terminal ID also functions as a user ID (information for identification of a user). 
     Prescribed application software (which is simply referred to as an “application” below) is installed in portable terminal  80 , and portable terminal  80  exchanges information with each of server  30 , HEMS-GW  60  and data center  70  through the application. Portable terminal  80  wirelessly communicates with each of server  30 , HEMS-GW  60  and data center  70 , for example, through the Internet. A user can transmit information representing a state and a schedule of the user to data center  70  by operating portable terminal  80 . Exemplary information representing a state of the user includes information indicating whether or not the user is in a condition of being ready for addressing DR. Exemplary information representing the schedule of the user includes time of departure of a POV from home or a drive plan of a MaaS vehicle. Each of server  30  and data center  70  stores the information received from portable terminal  80  as being distinguished for each terminal ID. 
     Server  10  and server  30  can communicate with each other, for example, through a virtual private network (VPN). Each of servers  10  and  30  can obtain power market information (for example, information on trading of electric power), for example, through the Internet. A protocol of communication between server  10  and server  30  may be OpenADR. Server  30  and data center  70  can communicate with each other, for example, through the Internet. A protocol of communication between server  30  and data center  70  may be OpenADR. Server  30  can obtain information on a user from data center  70 . Each of server  30  and data center  70  can communicate with HEMS-GW  60 , for example, through the Internet. A protocol of communication between each of server  30  and data center  70  and HEMS-GW  60  may be OpenADR. 
     Though server  30  and EVSE  40  do not communicate with each other in this embodiment, server  30  and EVSE  40  may communicate with each other. Server  30  may communicate with vehicle  50  with EVSE  40  being interposed. EVSE  40  may communicate with an EVSE management cloud. A protocol of communication between EVSE  40  and the EVSE management cloud may be open charge point protocol (OCPP). 
     Server  30  sequentially obtains from each vehicle  50 , information representing a state or schedule of each vehicle  50  (for example, a position of the vehicle, an ON/OFF state of a start switch, a state of connection of the charging cable, a state of the battery, a charging schedule, a condition for charging, a power feed schedule, a condition for power feed, a schedule of travel, and a condition for travel) under the control thereof and stores the information. The start switch is a switch for starting a vehicle system, and generally referred to as a “power switch” or an “ignition switch.” The state of connection of the charging cable is information on whether or not connector  43  of charging cable  42  is connected to inlet  110 . The state of the battery is information on a value of an SOC of battery  130  and information indicating whether or not battery  130  is being charged. The charging schedule is information indicating time of start and end of scheduled external charging. The condition for charging may be a condition for scheduled external charging (for example, charging power) or a condition for external charging that is currently ongoing (for example, charging power and a remaining time period of charging). The power feed schedule is information indicating time of start and end of scheduled external power feed. The condition for power feed may be a condition for scheduled external power feed (for example, feed power) or a condition for external power feed that is currently ongoing (for example, feed power and a remaining time period for power feed). The schedule of travel is information indicating time of start and end of scheduled travel. The condition for travel may be a condition for scheduled travel (for example, a travel route and a travel distance) or a condition for travel that is currently ongoing (for example, a traveling speed and a remaining distance of travel). 
     Server  10  levels electric power by using demand response (DR). When server  10  levels electric power, initially, the server transmits a signal (which is also referred to as a “DR participation request” below) requesting participation into DR to each aggregator server (including server  30 ). The DR participation request includes a region of interest of DR, a type of DR (for example, DR suppression or DR increase), and a DR period. When server  30  receives a DR participation request from server  10 , it calculates an adjustable DR amount (that is, an amount of electric power that can be adjusted in accordance with DR) and transmits the amount to server  10 . Server  30  can calculate the adjustable DR amount, for example, based on a total of DR capacities of demand sides under the control thereof. The DR capacity refers to a capacity secured by a demand side for DR. 
     Server  10  determines a DR amount (that is, an amount of power regulation asked to an aggregator) for each aggregator based on the adjustable DR amount received from each aggregator server and transmits a signal (which is also referred to as a “DR execution instruction” below) instructing each aggregator server (including server  30 ) to execute DR. The DR execution instruction includes a region of interest of DR, a type of DR (for example, DR suppression or DR increase), a DR amount for the aggregator, and a DR period. When server  30  receives the DR execution instruction, it allocates the DR amount to each vehicle  50  that can address DR among vehicles  50  under the control thereof, generates a DR signal for each vehicle, and transmits the DR signal to each vehicle  50 . The DR signal may be a price signal that urges a user of vehicle  50  to regulate supply and demand or a charging command or a power feed command for server  30  to directly control vehicle  50 . The price signal may include a type of DR (for example, DR suppression or DR increase), a DR amount for vehicle  50 , a DR period, and incentive information. The price signal may be transmitted to portable terminal  80  instead of or in addition to vehicle  50 . When vehicle  50  permits remote control (for example, dispatching by server  30 ), server  30  can directly control vehicle  50  by transmitting a charging command or a power feed command to vehicle  50 . 
     ECU  150  receives a DR signal through communication equipment  180  from the outside of the vehicle. When ECU  150  receives the DR signal, a user of vehicle  50  can contribute to regulation of supply and demand of electric power requested by an electric utility (for example, an electric power utility company or an aggregator) by carrying out external charging or external power feed in accordance with the DR signal by using EVSE  40  and vehicle  50 . The electric utility can request the user of vehicle  50  to regulate supply and demand of electric power by transmitting the DR signal. The DR signal may be transmitted from server  30  to vehicle  50  in response to a DR execution instruction as described above. The DR signal may also be transmitted from server  30  to vehicle  50  based on power market information (see, for example,  FIG. 6  which will be described later). In this embodiment, when the user of vehicle  50  has contributed to regulation of supply and demand of electric power requested by the electric utility, an incentive in accordance with contribution is paid to the user of vehicle  50  by the electric utility based on an agreement between the user of vehicle  50  and the electric utility. 
     An electric utility measures contribution with any method. The electric utility may find a contribution based on a measurement value from smart meter  11 . VGI system  1  may include, in addition to smart meter  11 , a wattmeter (for example, a not-shown smart meter) that measures a contribution. The electric utility may find a contribution based on a measurement value from a wattmeter (not shown) contained in EVSE  40 . The electric utility may find a contribution based on a measurement value from a sensor (for example, monitoring module  121  or  131 ) mounted on vehicle  50 . A portable charging cable may be provided with a metering function and the electric utility may find a contribution based on an amount of electric power measured by the charging cable. A user ID may be provided for each charging cable and the user ID may automatically be transmitted from the charging cable to a server (for example, server  10  or  30 ) of the electric utility when the user uses the charging cable. By doing so, the electric utility can identify which user has carried out charging and discharging. 
     Vehicle  50  shown in  FIG. 2  is electrically connected to outdoor EVSE  40  through charging cable  42  while it is parked in a parking space of a residence (for example, a user&#39;s house). EVSE  40  is a non-public charging facility used only by a user and a family member of the user. In this embodiment, EVSE  40  is a charging facility adapted to backfeeding (that is, a charging and discharging facility). As connector  43  of charging cable  42  connected to EVSE  40  is connected to inlet  110  of vehicle  50 , vehicle  50  and EVSE  40  can communicate with each other and electric power can be supplied and received between EVSE  40  and vehicle  50 . Power supply circuit  41  included in EVSE  40  is electrically connected to power grid PG. For example, as electric power is supplied from power grid PG through power supply circuit  41  and charging cable  42  to vehicle  50 , battery  130  is externally charged. As vehicle  50  carries out external power feed to EVSE  40 , electric power can be backfed from vehicle  50  through charging cable  42  and power supply circuit  41  to power grid PG. Power supply circuit  41  converts electric power supplied from power grid PG into electric power suitable for external charging and converts electric power supplied from vehicle  50  into electric power suitable for backfeeding. 
     Power supply circuit  41  is connected to power grid PG provided by the electric power utility company with smart meter  11  being interposed. Smart meter  11  measures an amount of electric power supplied from EVSE  40  to vehicle  50 . Smart meter  11  may also measure an amount of electric power backfed from vehicle  50  to EVSE  40 . Smart meter  11  measures an amount of power usage each time a prescribed time period elapses (for example, each time thirty minutes elapse), stores the measured amount of power usage, and transmits the measured amount of power usage to server  10  and HEMS-GW  60 . For example, IEC (DLMS/COSEM) can be adopted as a protocol for communication between smart meter  11  and server  10 . Server  10  transmits at any time, a value of measurement by smart meter  11  to server  30 . Server  10  may transmit the measurement value regularly or upon request from server  30 . 
     HEMS-GW  60  transmits information on energy management (for example, information representing a state of use of electric power) to each of server  30 , data center  70 , and portable terminal  80 . HEMS-GW  60  receives a value of measurement of the amount of electric power from smart meter  11 . Smart meter  11  and HEMS-GW  60  may communicate with each other in any type of communication, and the type of communication may be a 920-MHz-band low-power wireless communication or power line communication (PLC). HEMS-GW  60  and EVSE  40  can communicate with each other, for example, through a local area network (LAN). The LAN may be wired or wireless LAN. Standards of communication between HEMS-GW  60  and EVSE  40  may be any of ECHONET Lite, smart energy profile (SEP)  2 . 0 , and KNX. 
     Communication equipment  180  mounted on vehicle  50  communicates with EVSE  40  through charging cable  42 . Communication between EVSE  40  and vehicle  50  may be of any type, and for example, controller area network (CAN) or PLC may be adopted. Standards of communication between EVSE  40  and vehicle  50  may be ISO/IEC15118 or IEC61851. 
     Communication equipment  180  wirelessly communicates with server  30 , for example, through a mobile communication network (telematics). A signal exchanged between vehicle  50  and server  30  may be encrypted by a scheme designated by an aggregator. In this embodiment, communication equipment  180  and portable terminal  80  wirelessly communicate with each other. ECU  150  ( FIG. 1 ) can control portable terminal  80  through wireless communication to give a notification to a user. Communication equipment  180  and portable terminal  80  may communicate with each other through short-range communication such as Bluetooth® (for example, direct communication in a vehicle or within an area around the vehicle). 
       FIG. 3  is a diagram showing a power grid, a plurality of pieces of EVSE, and a plurality of vehicles included in the power management system according to this embodiment. Referring to  FIG. 3 , VGI system  1  includes EVSE  40 A to  401 , vehicles  50 A to  50 D, and power grid PG. Vehicles  50 A to  50 D include batteries  130 A to  130 D, respectively. Each of batteries  130 A to  130 D is capable of both of external charging and external power feed. Each of pieces of EVSE  40 A to  401  corresponds to an exemplary “power facility” according to the present disclosure. 
     Power grid PG supplies electric power to each of pieces of EVSE  40 A to  401 . Each of vehicles  50 A to  50 D can electrically be connected to power grid PG through any of pieces of EVSE  40 A to  401 . In the example shown in  FIG. 3 , vehicles  50 A,  50 B,  50 C, and  50 D are electrically connected to power grid PG through EVSE  40 A,  40 D,  40 E, and  40 G, respectively. Power grid PG can supply electric power to vehicles  50 A to  50 D through EVSE  40 A,  40 D,  40 E, and  40 G, respectively. 
     In the power management system (VGI system  1 ) according to this embodiment, the user of vehicle  50  can receive an incentive by meeting the request from server  30 . All users, however, do not place highest priority on the incentive. Some users may prefer suppression of deterioration of battery  130  to reception of the incentive. 
     In the power management system (VGI system  1 ) according to this embodiment, vehicle  50 , server  30 , and portable terminal  80  are configured as described below, so that server  30  can a request a user of vehicle  50  to regulate supply and demand of electric power with attention being paid to a user who desires suppression of deterioration of battery  130 .  FIG. 4  is a diagram showing a detailed configuration of ECU  150  of vehicle  50 , server  30 , and portable terminal  80 . 
     Referring to  FIG. 4 , portable terminal  80  includes a controller  81 , a storage  82 , a communication apparatus  83 , and a touch panel display (TPD)  84 . Controller  81  includes a processor, performs prescribed information processing, and controls communication apparatus  83  and TPD  84 . Storage  82  can store various types of information. Communication apparatus  83  includes various communication I/Fs. Controller  81  communicates with the outside through communication apparatus  83 . Portable terminal  80  is carried by a user of vehicle  50  and TPD  84  gives a notification (for example, representation) to a user of vehicle  50 . The notification may be provided by voice and sound, without being limited to representation. 
     Server  30  can communicate with each of communication equipment  180  of vehicle  50  and portable terminal  80 . Server  30  includes an information manager  301 , an estimator  302 , a selector  303 , a scheduler  304 , a request processor  305 , and an incentive manager  306 . In server  30  according to this embodiment, each component above is implemented by the processor of controller  31  shown in  FIG. 2  and a program executed by the processor. Without being limited as such, each component above may be implemented by dedicated hardware (electronic circuitry). 
     ECU  150  includes an information manager  501  and a charging and discharging controller  502 . In ECU  150  according to this embodiment, each component above is implemented by processor  151  shown in  FIG. 1  and a program executed by processor  151 . Without being limited as such, each component above may be implemented by dedicated hardware (electronic circuitry). 
     Information manager  501  of ECU  150  successively transmits information representing a state or a schedule of vehicle  50  described previously to server  30 . Information manager  501  can obtain the state of vehicle  50  based on outputs from various sensors mounted on vehicle  50 . Information manager  301  of server  30  has storage  32  store information received from vehicle  50  in association with a vehicle ID of vehicle  50 . 
     Estimator  302  of server  30  estimates next departure time of vehicle  50  based on history data included in the information received from the vehicle. In this embodiment, estimator  302  learns a time period for which vehicle  50  stays (that is, a time period from arrival of vehicle  50  at a charging location until departure from the charging location) from history data of vehicle  50 . Information manager  301  has storage  32  store history data to be used for learning of the time period of stay among pieces of information received from vehicle  50 , as being distinguished for each charging location. The history data used for learning of the time period of stay is also referred to as “training data” below. In the example shown in  FIG. 2 , a user&#39;s house is the charging location. In this embodiment, history data on a position, arrival time, and departure time of vehicle  50  is adopted as training data. The position of vehicle  50  may be a position detected by the position sensor described previously. Arrival time of vehicle  50  may be timing of connection of connector  43  of charging cable  42  connected to EVSE  40  to inlet  110  of vehicle  50 . Departure time of vehicle  50  may be timing of turn-on of the start switch of vehicle  50 . Estimator  302  has storage  32  store a result of learning (that is, the time period of stay that has been learnt) as being distinguished for each charging location. Any learning method is applicable. Artificial intelligence (AI) may be used for learning. 
     In this embodiment, when vehicle  50  arrives at a next charging location, estimator  302  obtains a time period of stay learnt for that next charging location from storage  32 . Then, estimator  302  estimates next departure time based on next arrival time (that is, time of arrival of vehicle  50  at the next charging location) and a time period of next stay (that is, the learnt time period of stay). Estimator  302  may estimate as next departure time, timing of lapse of the time period of next stay since next arrival time. 
     Though details will be described later (see  FIG. 6 ), when server  30  is requested to regulate supply and demand of electric power from the outside (for example, an electric power utility company or a power market), server  30  requests each vehicle  50  under the control thereof to regulate electric power in a procedure as shown below. Initially, selector  303  selects vehicles  50  in number necessary for meeting the request from the outside from among a plurality of vehicles  50  under the control thereof. Each vehicle  50  selected by selector  303  is also referred to as a “DR vehicle” below. Scheduler  304  makes a charging and discharging control schedule (which is simply referred to as a “schedule” below) for battery  130  of each DR vehicle. The schedule may be a charging schedule, a power feed schedule, or a charging suppression schedule. The charging suppression schedule refers to a schedule that shows a period for which charging is restricted (that is, time of start and end of restriction). Examples of charging restriction include prohibition of charging and restriction of charging power (that is, prohibition of charging with prescribed electric power or higher). Each of the DR vehicle selected by selector  303  and the schedule made by scheduler  304  is stored in storage  32  of server  30 . Request processor  305  transmits a DR signal for requesting electric power regulation in accordance with the schedule made by scheduler  304  to the user of each DR vehicle. The DR signal requests the user of the DR vehicle to control at least one of external charging and external power feed in accordance with the schedule. The DR signal may be transmitted to communication equipment  180  mounted on the DR vehicle or to portable terminal  80  carried by the user of the DR vehicle. Each of communication equipment  180  and portable terminal  80  corresponds to the communication apparatus registered in server  30  in association with the user of vehicle  50 . 
     The user can receive an incentive from an aggregator by controlling at least one of external charging and external power feed in accordance with the DR signal or permitting remote control of vehicle  50  by server  30  during a period indicated in the schedule. Incentive manager  306  has storage  32  store incentive information of each user as being distinguished based on a user ID. Incentive information includes a unit price of the incentive and an acquired amount of incentive. Incentive manager  306  manages for each user, the unit price of the incentive given to the user at the time when the user meets the request from request processor  305 . Incentive manager  306  can change the unit price of the incentive for each user. Any unit price of the incentive may be set, and the unit price of the incentive may be a unit price per one DR of the incentive paid for participation into DR, a unit price per unit electric power amount of the incentive paid for a regulated amount of electric power, or a unit price per unit time of the incentive paid for a time period for which a vehicle is bound. Incentive manager  306  has storage  32  store for each user, also an acquired amount of incentive (that is, the total amount of incentive acquired by the user) in addition to the unit price of the incentive. 
     When information manager  501  receives the DR signal described above from server  30 , the DR signal is stored in storage  153 . Charging and discharging controller  502  carries out charging and discharging control of battery  130  by controlling charger-discharger  120 . Though remote control of charging and discharging controller  502  is prohibited in principle, it can remotely be controlled by server  30  during a DR period indicated in the schedule included in the DR signal within storage  153 . The DR period corresponds to a period from DR start time until DR end time. While charging and discharging controller  502  is remotely controllable, server  30  can directly control charging and discharging controller  502  by transmitting a charging command or a power feed command to vehicle  50 . Information manager  501  may suppress unauthorized remote control (for example, remote control by a component other than server  30 ) by performing prescribed authentication of a received command and excluding the unauthorized command. Permission and prohibition of remote control of charging and discharging controller  502  may be set by a user of vehicle  50  through input apparatus  160  or portable terminal  80 . 
     Storage  32  of server  30  stores vehicle information for each vehicle and user information for each user of vehicle  50 .  FIG. 5  is a diagram for illustrating details of vehicle information and user information held by server  30 . 
     Referring to  FIG. 5  together with  FIG. 4 , the user information in storage  32  includes mode information which will be described below. Each of input apparatus  160  mounted on vehicle  50  and TPD  84  of portable terminal  80  carried by the user of vehicle  50  accepts input from the user of vehicle  50 . Each of notification apparatus  170  ( FIG. 1 ) of vehicle  50  and TPD  84  of portable terminal  80  may issue a request for input of any of an incentive prioritized mode and a battery life prioritized mode to the user of vehicle  50  through representation or voice and sound. When the user of vehicle  50  inputs any mode to input apparatus  160  or TPD  84  in response to the request, ECU  150  of vehicle  50  or controller  81  of portable terminal  80  controls storage  153  or storage  82  to store the mode information (that is, information indicating the mode selected by the user) and transmits the mode information to server  30 . Server  30  controls storage  32  to store the received mode information in association with a user ID. In this embodiment, the mode information corresponds to exemplary “first desire information” and exemplary “second desire information” according to the present disclosure. Selection of the battery life prioritized mode by the user means that the user desires suppression of deterioration of battery  130  but does not desire acquisition of the incentive. Selection of the incentive prioritized mode by the user means that the user does not desire suppression of deterioration of battery  130  but desires acquisition of the incentive. In this embodiment, input apparatus  160  and ECU  150  mounted on vehicle  50  function as the “user terminal” according to the present disclosure. 
     The user information further includes the incentive information described previously. Incentive manager  306  sets a higher unit price of the incentive for a user lower in level of the user&#39;s desire for suppression of deterioration of battery  130 , by referring to the mode information. Specifically, incentive manager  306  sets the unit price of the incentive for the user who has selected the incentive prioritized mode to be higher than the unit price of the incentive for the user who has selected the battery life prioritized mode. 
     The vehicle information in storage  32  includes exclusion information, DR participation priority, next departure time, and a schedule. The exclusion information is information for selection of a vehicle not suitable as a DR vehicle. In this embodiment, the SOC of battery  130  and the number of times of charging per unit period are adopted as exclusion information. A first threshold value, a second threshold value, and an upper limit value which will be described later are also included in the exclusion information. 
     Though details will be described later, selector  303  determines the DR participation priority for each vehicle based on the mode information described previously. Vehicle  50  higher in DR participation priority is more likely to be selected in selection of the DR vehicle (see  FIG. 7  which will be described later). Next departure time is estimated by estimator  302  with the method described previously and stored in storage  32 . Scheduler  304  makes a schedule for each vehicle based on the mode information and next departure time (see  FIG. 6  which will be described later). 
       FIG. 6  is a flowchart showing processing performed by server  30  when an aggregator trades electric power in a power market. Processing shown in this flowchart is started in response to input by the aggregator of contents of electric power regulation requested in the power market to server  30  when regulation of supply and demand of power grid PG is requested in the power market. Contents of electric power regulation input to server  30  are also referred to as “request contents” below. 
     Referring to  FIG. 6  together with  FIGS. 1 to 5 , in a step (which is simply denoted as “S” below)  11 , controller  31  of server  30  obtains request contents (that is, contents of electric power regulation) input by the aggregator. The request contents include a type of electric power regulation (for example, a request for external charging or a request for external power feed), an amount of electric power regulation, and a request period. 
     In S 12 , selector  303  of server  30  selects a DR vehicle to which a request for electric power regulation is to be issued, from among vehicles  50  under the control thereof.  FIG. 7  is a flowchart showing details of processing involved with selection of a DR vehicle made in S 12  in  FIG. 6 . 
     Referring to  FIG. 7  together with  FIGS. 1 to 6 , in S 21 , selector  303  of server  30  excludes an unsuitable vehicle (that is, a vehicle not suitable as the DR vehicle) from candidates for the DR vehicle based on the request contents obtained in  511  in  FIG. 6  and the mode information and the exclusion information ( FIG. 5 ) described previously. In an initial stage, all vehicles  50  under the control of the aggregator are included in candidates for the DR vehicle. Thereafter, in S 16  in  FIG. 6  which will be described later, candidates for the DR vehicle may be narrowed down. Vehicle  50  of a user who has selected the battery life prioritized mode is also referred to as a “first vehicle” below. Vehicle  50  of a user who has selected the incentive prioritized mode is also referred to as a “second vehicle.” Selector  303  can determine which of the first vehicle and the second vehicle each vehicle  50  under the control thereof falls under, based on the mode information. Selector  303  sets the upper limit value of the number of times of charging per unit period for each vehicle, based on the mode information. In this embodiment, for the first vehicle, a prescribed number is set as the upper limit value, and for the second vehicle, “none” is set as the upper limit value. The prescribed number corresponds to the threshold value for suppression of progress of deterioration of battery  130  due to repeated charging. 
     In this embodiment, the number of times of charging per one day is adopted as the number of times of charging per unit period. Ten times is adopted as the upper limit value set for the first vehicle. A process from start of charging until stop of charging is counted as one charging. How to count the number of times of charging will be described below with reference to  FIGS. 8 and 9 .  FIG. 8  is a diagram showing an exemplary charging schedule in which the number of times of charging is set to one. Referring to  FIG. 8 , in this charging schedule, charging is started at timing t 1  and stopped at timing t 2 . Therefore, external charging in vehicle  50  in accordance with the charging schedule shown in  FIG. 8  increments the number of times of charging of battery  130  by one.  FIG. 9  is a diagram showing an exemplary charging schedule in which the number of times of charging is set to five. Referring to  FIG. 9 , in this charging schedule, charging is intermittently carried out. First charging is started at timing t 1  and stopped at timing t 21 . Second charging is started at timing t 11  and stopped at timing t 22 . Third charging is started at timing t 12  and stopped at timing t 23 . Fourth charging is started at timing t 13  and stopped at timing t 24 . Fifth charging is started at timing t 14  and stopped at timing t 2 . Therefore, external charging in vehicle  50  in accordance with the charging schedule shown in  FIG. 9  increments the number of times of charging of battery  130  by five. 
     Referring again to  FIG. 7 , in S 21 , selector  303  excludes the first vehicle of which the number of times of charging per one day has exceeded ten times from candidates for the DR vehicle. The upper limit value for the first vehicle may be fixed or variable depending on the request contents. 
     When the request contents obtained in  511  in  FIG. 6  request for external power feed, in S 21 , selector  303  excludes vehicle  50  in which the SOC of battery  130  is smaller than a prescribed first threshold value from candidates for the DR vehicle. Though any first threshold value can be set, for example, an SOC value selected within a range not lower than 15% and not higher than 50% may be set. When the request contents obtained in  511  in  FIG. 6  request for external charging, in S 21 , selector  303  excludes vehicle  50  in which the SOC of battery  130  exceeds a prescribed second threshold value from candidates for the DR vehicle. Though any second threshold value can be set, an SOC value selected, for example, within a range not lower than 50% and not higher than 85% may be set. 
     In S 22 , selector  303  determines the DR participation priority of each vehicle  50  which is the candidate for the DR vehicle, based on the request contents obtained in  511  in  FIG. 6  and the mode information ( FIG. 5 ) described previously. When the request contents obtained in  511  in  FIG. 6  request for external power feed, selector  303  sets the DR participation priority of the first vehicle to be higher than the DR participation priority of the second vehicle. When the request contents obtained in  511  in  FIG. 6  request for external charging, selector  303  sets the DR participation priority of the second vehicle to be higher than the DR participation priority of the first vehicle. The first vehicles may be identical in DR participation priority, or varied in DR participation priority in accordance with a reference other than the mode information. For example, the SOC of battery  130  may be adopted as the reference other than the mode information. In selection of a DR vehicle to which a request for external power feed is to be issued, selector  303  may set the DR participation priority of the first vehicle higher in SOC of battery  130  to be higher. In selection of a DR vehicle to which a request for external charging is to be issued, selector  303  may set the DR participation priority of the first vehicle lower in SOC of battery  130  to be higher. The second vehicles may also be identical in DR participation priority, or varied in DR participation priority in accordance with a reference other than the mode information, similarly to the first vehicles. 
     In S 23 , selector  303  selects a DR vehicle in accordance with the DR participation priority of each vehicle  50  determined in S 22 . Selector  303  selects a prescribed number (more specifically, a number necessary for meeting the request contents) of DR vehicles from among candidates for the DR vehicle in the order of higher DR participation priority.  FIG. 10  is a diagram for illustrating selection of a DR vehicle. 
     Referring to  FIG. 10 , when the request contents request for external charging, selector  303  preferentially makes selection from among the second vehicles (that place priority on the incentive). Specifically, when the request contents request for external charging, vehicle  50  lower in level of the user&#39;s desire for suppression of deterioration of battery  130  (that is, higher in level of the user&#39;s desire for acquisition of the incentive) is preferentially sequentially selected from among vehicles  50  in which the SOC of battery  130  is equal to or smaller than the second threshold value. When there are a sufficient number of the second vehicles, all selected DR vehicles fall under the second vehicles. When there are an insufficient number of the second vehicles, the selected DR vehicles include both of the first vehicles and the second vehicles. When the request contents request for external power feed, selector  303  preferentially makes selection from among the first vehicles (that place priority on battery life). Specifically, when the request contents request for external power feed, vehicle  50  higher in level of the user&#39;s desire for suppression of deterioration of battery  130  (that is, lower in level of the user&#39;s desire for acquisition of the incentive) is preferentially sequentially selected from among vehicles  50  in which the SOC of battery  130  is equal to or larger than the first threshold value. When there are a sufficient number of the first vehicles, all selected DR vehicles fall under the first vehicles. When there are an insufficient number of the first vehicles, the selected DR vehicles include both of the first vehicles and the second vehicles. When the first vehicle (that places priority on battery life) is preferentially selected, an opportunity for the user of the second vehicle (that places priority on the incentive) to acquire the incentive may be lost. Then, incentive manager  306  sets the unit price of the incentive of the user of the second vehicle (that places priority on the incentive) to be higher than the unit price of the incentive for the user of the first vehicle (that places priority on battery life). Thus, the user of the second vehicle (that places priority on the incentive) is more likely to acquire the higher incentive at the sacrifice of susceptibility of battery  130  to deterioration. Consequently, fairness among users can be ensured. 
     When there are a large number of vehicles  50  equal in DR participation priority and a prescribed number of DR vehicles cannot be selected only based on the DR participation priority, selector  303  may narrow down candidates for the DR vehicle based on the DR participation priority and thereafter select the DR vehicles based on an arbitrary reference (or randomly) from among a plurality of vehicles  50  equal in DR participation priority. 
     As the processing in S 23  in  FIG. 7  is performed, the processing in S 12  in  FIG. 6  ends. Thereafter, the process proceeds to S 13  in  FIG. 6 . Referring again to  FIG. 6  together with  FIGS. 1 to 5 , in S 13 , scheduler  304  of server  30  makes a schedule for each DR vehicle selected in S 12 . When the request contents obtained in  511  request for external power feed, scheduler  304  makes a power feed schedule that indicates time to start and quit external power feed. When the request contents obtained in  511  request for external charging, scheduler  304  makes a charging schedule that indicates time to start and quit external charging. Scheduler  304  makes a schedule for each DR vehicle based on the mode information and next departure time ( FIG. 5 ). 
     In making the charging schedule, scheduler  304  makes the charging schedule such that a time lag between charging end time in the charging schedule and next departure time is smaller in a DR vehicle higher in level of the user&#39;s desire for suppression of deterioration of battery  130  or a DR vehicle lower in level of the user&#39;s desire for acquisition of the incentive.  FIG. 11  is a diagram for illustrating making of a charging schedule. Referring to  FIG. 11  together with  FIGS. 1 to 5 , for example, when DR vehicles selected in S 12  include the first vehicle (that places priority on battery life) and the second vehicle (that places priority on the incentive) identical in next departure time, scheduler  304  sets a charging schedule Sc 11  for the second vehicle to precede a charging schedule Sc 12  for the first vehicle. A time lag (that is, a time period T 2 ) between charging end time and next departure time of charging schedule Sc 12  is shorter than a time lag (that is, a time period T 1 ) between charging end time and next departure time of charging schedule Sc 11 . Such schedule setting can achieve suppression of battery  130  of the first vehicle being left stand in the high SOC state and deterioration of battery  130  of the user who has selected the battery life prioritized mode. When there are a large number of first vehicles among DR vehicles selected in S 12  and deterioration of batteries  130  of all first vehicles cannot be suppressed, scheduler  304  may select the first vehicle in which deterioration of battery  130  is to be suppressed based on an arbitrary reference (or randomly). 
     In making the power feed schedule, scheduler  304  makes the power feed schedule such that external power feed is started earlier in the DR vehicle higher in level of the user&#39;s desire for suppression of deterioration of battery  130 . Specifically, scheduler  304  sets the power feed schedule for the first vehicle to precede the power feed schedule for the second vehicle. When there are a plurality of first vehicles among DR vehicles selected in S 12 , scheduler  304  may make the power feed schedule for each first vehicle such that external power feed of the first vehicle higher in SOC of battery  130  is started earlier. When there are a plurality of second vehicles among DR vehicles selected in S 12 , scheduler  304  may make the power feed schedule for each second vehicle such that external power feed of the second vehicle higher in SOC of battery  130  is started earlier. 
     Referring again to  FIG. 6  together with  FIGS. 1 to 5 , in S 14 , controller  31  controls communication apparatus  33  to transmit the schedule made in S 13  to the user of each DR vehicle and to request the user to give an answer as to whether or not the user approves the schedule. The schedule may be transmitted to communication equipment  180  ( FIG. 1 ) mounted on the DR vehicle or to portable terminal  80  ( FIG. 2 ) carried by the user of the DR vehicle. 
     In S 15 , controller  31  determines whether or not all users to which the schedule had been sent have given answers indicating approval of the schedule. This determination is made, for example, at timing of reception of answers from all users to which the schedule had been transmitted or timing of lapse of a prescribed time period since transmission of the schedule. In this embodiment, a user who has not yet transmitted the answer even after lapse of the prescribed time period since transmission of the schedule is handled similarly to a user who has given an answer to the effect that the user does not approve the schedule. 
     When determination as NO is made in S 15  (at least one user has not approved the schedule), in S 16 , controller  31  excludes a vehicle belonging to the user who has not approved the schedule from candidates for the DR vehicle. Thereafter, the process returns to S 12 . The vehicle excluded in S 16  is not selected in S 12  (see  FIG. 7 ). While determination as NO is made in S 15 , S 12  to S 16  are repeatedly performed. 
     When determination as YES is made in S 15  (all users have approved the schedule), in S 17 , controller  31  notifies the aggregator of completion of preparation for electric power trading through a not-shown notification apparatus (for example, a touch panel display). Approval of the schedule by the user of each DR vehicle means that the user of each DR vehicle and the aggregator have reached a provisional agreement. The provisional agreement is a promise to the user of the DR vehicle by the aggregator, of payment of the incentive to the user who meets the request from the aggregator. 
     As DSR (the DR vehicle) for regulation of electric power is secured as above, the aggregator can trade electric power in the power market, for example, through Japan Electric Power Exchange (JEPX). The aggregator may also make a bid. When trading ends, the aggregator inputs a result (done/not done) of trading into server  30 . 
     After controller  31  of server  30  performs notification processing in S 17 , in S 18 , it waits for input from the aggregator. Then, when the result (done/not done) of trading is input from the aggregator (YES in S 18 ), in S 19 , controller  31  determines whether or not trading of electric power was done. 
     When trading of electric power was done (YES in S 19 ), in S 191 , request processor  305  of server  30  transmits a DR signal described previously to the user of each DR vehicle. As the user of each DR vehicle receives the DR signal, a formal agreement is concluded between the user of each DR vehicle and the aggregator. The formal agreement is a promise by the user of each DR vehicle to the aggregator that the user has each DR vehicle stand by such that server  30  can remotely control external charging and external power feed of each DR vehicle during the DR period indicated in the schedule in each DR signal. Conclusion of the formal agreement finalizes the promise in the provisional agreement described previously. The user who has received the DR signal can receive the incentive from the aggregator by having the DR vehicle stand by as above. On the other hand, a penalty is imposed on a user who has broken the promise. When trading of electric power was not done (NO in S 19 ), in S 192 , request processor  305  of server  30  notifies the user of each DR vehicle that trading was not done. The provisional agreement described previously is withdrawn by this notification. 
       FIG. 12  is a flowchart showing charging and discharging control of battery  130  in vehicle  50  finalized as the DR vehicle. Processing shown in this flowchart is repeatedly performed by ECU  150  during the DR period indicated in the schedule included in the DR signal. When the user receives the DR signal, vehicle  50  belonging to that user is finalized as the DR vehicle, and when the DR period elapses, the DR vehicle returns to a non-DR vehicle (that is, vehicle  50  which is not the DR vehicle). 
     Referring to  FIG. 12  together with  FIGS. 1 to 5 , in S 31 , charging and discharging controller  502  ( FIG. 4 ) of ECU  150  determines whether or not battery  130  is in a chargeable and dischargeable state based on outputs from various sensors. For example, charging and discharging controller  502  checks a state of connection of charging cable  42 , and when electrical connection between the DR vehicle and EVSE  40  is insufficient, the charging and discharging controller determines that battery  130  is not in the chargeable and dischargeable state. When an abnormal condition (for example, communication abnormality or circuit abnormality) occurs in at least one of the DR vehicle and EVSE  40  as well, the charging and discharging controller determines that battery  130  is not in the chargeable and dischargeable state. 
     When battery  130  is in the chargeable and dischargeable state (YES in S 31 ), in S 32 , ECU  150  determines whether or not it has received a command for charging and discharging control from server  30 . When the ECU has received the command from server  30  (YES in S 32 ), in S 33 , charging and discharging controller  502  carries out charging and discharging control of battery  130  in accordance with the command. While ECU  150  continues to receive the command from server  30 , processing in S 31  to S 33  is repeated. Server  30  transmits a command to each DR vehicle in accordance with the schedule included in each DR signal. Therefore, control of charging and discharging controller  502  of each DR vehicle in accordance with the command from server  30  means control of external charging and external power feed of each DR vehicle in accordance with the schedule included in each DR signal. 
     For a period during which ECU  150  does not receive the command from server  30  (NO in S 32 ), ECU  150  waits for a command from server  30  while it repeats processing in S 31  and S 32 . 
     When determination as NO is made in S 31  (battery  130  is not in the chargeable and dischargeable state), the process proceeds to S 34 . In S 34 , ECU  150  controls notification apparatus  170  ( FIG. 1 ) to notify the user of the DR vehicle that battery  130  is not in the chargeable and dischargeable state. This notification may be given by TPD  84  of portable terminal  80 . Determination as NO in S 31  means that server  30  is unable to control external charging and external power feed of the DR vehicle by remote control (and a penalty is imposed on the user). 
       FIG. 13  is a flowchart showing charging and discharging control of battery  130  of a non-DR vehicle. Processing shown in this flowchart is repeatedly performed while the non-DR vehicle is parked. 
     Referring to  FIG. 13  together with  FIGS. 1 to 5 , in S 51 , whether or not a condition for starting external charging has been satisfied is determined. In this embodiment, when time to start charging that has been timer-programmed in ECU  150  comes, the condition for starting external charging is satisfied. When charging has not been timer-programmed in ECU  150 , connection of connector  43  of charging cable  42  connected to EVSE  40  to inlet  110  of vehicle  50  (see  FIG. 1 ) satisfies the condition for starting immediate charging. Immediate charging refers to external charging started immediately when preparation for external charging in vehicle  50  is completed. When a prescribed operation to start charging by the user onto EVSE  40  or vehicle  50  is performed as well, the condition for starting external charging is satisfied. Any operation to start charging can be set. The operation to start charging may be, for example, an operation to press a prescribed button by the user. 
     Though not shown in  FIG. 13 , when the condition for starting external charging is satisfied (YES in S 51 ), a start signal is input to ECU  150  and ECU  150  is started up. Started-up ECU  150  performs processing in S 52 . In S 52 , ECU  150  determines whether or not battery  130  is in the chargeable and dischargeable state. Processing in S 52  is the same, for example, as S 31  in  FIG. 12 . 
     When battery  130  is in the chargeable and dischargeable state (YES in S 52 ), in S 53 , charging and discharging controller  502  controls charger-discharger  120  to carry out external charging. Thereafter, in S 54 , charging and discharging controller  502  determines whether or not a condition for quitting external charging has been satisfied. While determination as NO is made in S 54 , external charging (S 53 ) is continued. Any condition for quitting external charging can be set. The condition for quitting external charging may be satisfied when the SOC of battery  130  is equal to or larger than a prescribed SOC value during external charging or when a user gives an instruction to stop charging during external charging. When the condition for quitting external charging has been satisfied (YES in S 54 ), the vehicle system (and ECU  150 ) enters a stop state (for example, a sleep mode) and thereafter the process proceeds to S 55 . When determination as NO is made in any of S 51  and S 52  as well, the process proceeds to S 55 . 
     In S 55 , whether or not the condition for starting external power feed has been satisfied is determined. In this embodiment, when a user performs a prescribed operation to start power feed onto EVSE  40  or vehicle  50 , the condition for starting external power feed is satisfied. Any operation to start power feed can be set. The operation to start power feed may be, for example, an operation to press a prescribed button by the user. 
     Though not shown in  FIG. 13 , when the condition for starting external power feed is satisfied (YES in S 55 ), a start signal is input to ECU  150  and ECU  150  is started up. Then, started-up ECU  150  performs processing in S 56 . In S 56 , ECU  150  determines whether or not battery  130  is in the chargeable and dischargeable state. Processing in S 56  is the same, for example, as S 31  in  FIG. 12 . 
     When battery  130  is in the chargeable and dischargeable state (YES in S 56 ), in S 57 , charging and discharging controller  502  controls charger-discharger  120  to carry out external power feed. Thereafter, in  558 , charging and discharging controller  502  determines whether or not a condition for quitting external power feed has been satisfied. While determination as NO is made in S 58 , external power feed (S 57 ) is continued. Any condition for quitting external power feed can be set. The condition for quitting external power feed may be satisfied when the SOC of battery  130  is equal to or smaller than a prescribed SOC value during external power feed. The condition for quitting external power feed may be satisfied when an amount of electric power (that is, an accumulated value of discharging power of battery  130 ) supplied from vehicle  50  to EVSE  40  in external power feed has exceeded a prescribed value. The condition for quitting external power feed may be satisfied when the user gives an instruction to stop power feed during external power feed. When the condition for quitting external power feed has been satisfied (YES in S 58 ), the vehicle system (and ECU  150 ) enters the stop state (for example, the sleep mode) and thereafter the process returns to S 51 . When determination as NO is made in any of S 55  and S 56  as well, the process returns to S 51 . 
     As described above, in the power management system (VGI system  1 ) according to this embodiment, server  30  obtains the mode information for each vehicle and makes selection (S 12  in  FIG. 6 ) of a DR vehicle and makes a schedule (S 13  in  FIG. 6 ) based on the obtained mode information. The mode information indicates a level of the user&#39;s desire (any of desiring and not desiring) for suppression of deterioration of battery  130  and a level of the user&#39;s desire (any of desiring and not desiring) for acquisition of the incentive. For a request that may cause deterioration of battery  130 , in selection of a DR vehicle, server  30  makes the first vehicle (that places priority on battery life) less likely to be selected. In making a schedule for the first vehicle, server  30  makes a schedule in which battery  130  is less likely to deteriorate. The power management system can issue a request for regulation of supply and demand of electric power to a user of vehicle  50  including battery  130  with attention being paid to a user who desires suppression of deterioration of battery  130 . 
     Though desire information (more specifically, mode information) is used for both of selection of a DR vehicle (S 12  in  FIG. 6 ) and making of a schedule (S 13  in  FIG. 6 ) in the embodiment, the desire information may be used for only any one of selection of a DR vehicle and making of a schedule. For example, in selection of a DR vehicle from among vehicles  50  electrically connected to power grid PG at the current time point for requesting the DR vehicle to participate in DR that is immediately carried out, server  30  may select a DR vehicle based on the desire information. 
     The mode information is adopted as the desire information in the embodiment. The mode information corresponds to information that indicates a desire level in two levels (priority on battery life or the incentive). The user selecting/not selecting the battery life prioritized mode corresponds to the user desiring/not desiring suppression of deterioration of the power storage. The user selecting/not selecting the incentive prioritized mode corresponds to the user desiring/not desiring acquisition of the incentive. The desire information, however, is not limited to information that indicates the desire level in two levels. The desire information may be information that indicates the desire level in three or more levels (for example, five levels) or information that indicates the desire level with continuous values from 0 to 100. Server  30  may carry out at least one of selection of a DR vehicle and making of a schedule so as to suppress deterioration of battery  130  more for a user higher in desire level. 
       FIG. 14  is a diagram for illustrating a modification of selection of a DR vehicle. In this modification, desire information that indicates the desire level with continuous values is adopted. A higher desire level shown in  FIG. 14  means a higher first desire level (that is, a level of the user&#39;s desire for suppression of deterioration of the power storage) and a lower second desire level (that is, a level of the user&#39;s desire for acquisition of the incentive). 
     Referring to  FIG. 14 , in requesting a DR vehicle to carry out external power feed, selector  303  sets higher DR participation priority for vehicle  50  higher in desire level. In selection of a DR vehicle to which a request for external power feed is to be issued, vehicle  50  higher in desire level is preferentially sequentially selected in accordance with the DR participation priority. As the SOC of battery  130  is lowered by external power feed, deterioration of battery  130  is suppressed. In requesting a DR vehicle to carry out external charging, selector  303  sets lower DR participation priority for vehicle  50  higher in desire level. In selection of a DR vehicle to which a request for external charging is to be issued, vehicle  50  lower in desire level is preferentially sequentially selected in accordance with the DR participation priority. By lowering a frequency of charging, deterioration of battery  130  is suppressed. Incentive manager  306  sets a higher unit price of the incentive for a user lower in desire level. Thus, in vehicle  50  lower in desire level, the user is more likely to acquire a higher incentive at the sacrifice of susceptibility of battery  130  to deterioration. Consequently, fairness among the users is ensured. Though not shown in  FIG. 14 , selector  303  may set a smaller upper limit value of the number of times of charging per unit period for vehicle  50  higher in desire level. 
     In the embodiment, server  30  obtains for each power storage, the desire information that indicates the first desire level (the level of desire for battery life) and the second desire level (the level of desire for acquisition of the incentive), preferentially selects the power storage of the user higher in second desire level (lower in first desire level) for a request for external charging, and preferentially selects the power storage of the user lower in second desire level (higher in first desire level) for a request for external power feed (see  FIG. 10 ). Without being limited as such, server  30  may obtain for each power storage, desire information that indicates only the second desire level and preferentially select the power storage of the user higher in second desire level for each request for external charging and external power feed. It is not essential to change the unit price of the incentive in accordance with the second desire level, and the unit price of the incentive may be constant. 
     In the embodiment, next departure time estimated by server  30  (more specifically, estimator  302 ) is used for making a charging schedule. Without being limited as such, server  30  may use next departure time (for example, time of departure of a POV from the house or a drive plan of a MaaS vehicle) obtained from the user for making the charging schedule. 
     In the embodiment, server  30  remotely controls vehicle  50  to control external charging and external power feed in accordance with a schedule. Remote control of vehicle  50  by server  30 , however, is not essential. ECU  150  mounted on vehicle  50  may control external charging and external power feed in accordance with the schedule (a request from request processor  305 ). 
     The power management system is not limited to VGI system  1  shown in  FIGS. 2 and 3 . The power management system may include a power facility that carries out only power feed with electric power supplied from power grid PG or a power facility that carries out only backfeeding to power grid PG. The power management system may include a vehicle capable only of external charging or a vehicle capable only of external power feed. The electric power utility company may be divided for each business sector. A power generation utility and a power transmission and distribution utility may belong to companies different from each other. In the embodiment, for electric power regulation requested in the power market, server  30  selects a DR vehicle, makes a schedule, and issues a request to the DR vehicle (see  FIG. 6 ). Without being limited as such, for electric power regulation requested by an electric power utility company, server  30  may select a DR vehicle, make a schedule, and issue a request for the DR vehicle. The server that selects a DR vehicle, makes a schedule, and issues a request to the DR vehicle is not limited to an aggregator server and any server that manages a vehicle is applicable. 
     A configuration of the vehicle is not limited to the configuration shown in  FIG. 1 . For example, in the configuration shown in  FIG. 1 , a charging apparatus capable only of external charging or a power feed apparatus capable only of external power feed may be adopted instead of charger-discharger  120 . The vehicle may be capable of wireless charging. The vehicle is not limited to a passenger vehicle but may be a bus or a truck. 
     The power management system described above may be applied to a mobile body other than the vehicle. The mobile body may be transportation means (a ship or an airplane) other than the vehicle or an unmanned mobile body (an automated guided vehicle (AGV), an agricultural implement, a movable robot, or a drone). The portable terminal may be carried by a manager of a mobile body (for example, a manager of a drone). 
     Though an embodiment of the present disclosure has been described, it should be understood that the embodiment disclosed herein is illustrative and non-restrictive in every respect. The scope of the present disclosure is defined by the terms of the claims and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.