Patent Publication Number: US-2021170902-A1

Title: Server and power management system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This nonprovisional application claims priority to Japanese Patent Application No. 2019-223034 filed with the Japan Patent Office on Dec. 10, 2019, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     Field 
     The present disclosure relates to a server and a power management system, 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. 2018-137886 discloses a power management system that sequentially selects a vehicle shorter in available time period (that is, a time period available for regulation of supply and demand of electric power) in selecting a vehicle to which a request for regulation of supply and demand of electric power is to be issued. The available time period corresponds to a time period from current time until charging start time (see paragraph [0031] of Japanese Patent Laying-Open No. 2018-137886). The available time period is calculated, for example, by subtracting a time period required for charging a power storage mounted on a vehicle to set a state of charge (SOC) thereof from a current value to a target value, from a time period from current time until scheduled travel start time. 
     SUMMARY 
     In the power management system described in Japanese Patent Laying-Open No. 2018-137886, a mobile body (more specifically, a vehicle) is selected based on the available time period. In selecting a mobile body, power run-out risk of the mobile body is not taken into consideration. Therefore, in the power management system described in Japanese Patent Laying-Open No. 2018 -137886, power run-out risk of the mobile body may be raised by regulation of supply and demand of electric power, which may compromise convenience of a user of the mobile body. The power run-out risk means a probability of occurrence of running out of electric power. Power run-out of a mobile body means that the mobile body is unable to travel due to decrease in electric power stored in a power storage of the mobile body. 
     The present disclosure was made to solve the problem above, and an object thereof is to provide a server and a power management system capable of suppressing excessively high power run-out risk of a power storage (and compromise of convenience of a user of the power storage) caused by regulation of supply and demand of electric power in requesting a user of the power storage to regulate supply and demand of electric power. 
     A server according to a first point of view of the present disclosure is usable 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 promote external charging, suppress external charging, or carry out external power feed in accordance with the made schedule. The server obtains power run-out information that indicates power run-out risk for each power storage and carries out at least one of selection of the power storage and making of the schedule in accordance with a type of a request (that is, any of promotion of external charging, suppression of external charging, and external power feed) based on the obtained power run-out 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. 
     The server carries out at least one of selection of the power storage and making of the schedule based on power run-out information. For example, for a request that will raise power run-out risk, in selection of a power storage, the server may make the power storage higher in power run-out risk less likely to be selected. The server may suppress increase in power run-out risk by adjusting time to start the request in making the schedule for the power storage high in power run-out risk. The server can thus adjust power run-out risk of each power storage based on at least one of selection of the power storage and making of the schedule. Therefore, in requesting the user of the power storage to regulate supply and demand of electric power, the server can suppress excessively high power run-out risk of the power storage due to regulation of supply and demand of electric power (and compromise of convenience of the user of the power storage) 
     When the selector selects a power storage requested to suppress external charging or carry out external power teed by the request processor, the selector may preferentially sequentially select the power storage lower in power run-out risk. 
     As the power storage carries out external charging, an SOC of the power storage increases and hence power run-out risk of the power storage is lowered. The 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%. When the power storage is requested to suppress external charging, lowering in power run-out risk of the power storage by external charging is restricted. Therefore, it becomes difficult for the power storage requested to suppress external charging to prevent power run-out risk from becoming excessively high. In this connection, according to the server, in selection by the selector of a power storage requested to suppress external charging, the selector preferentially sequentially selects a power storage lower in power run-out risk and hence excessively high power run-out risk of the power storage is suppressed. 
     As the power storage carries out external power feed, the SOC of the power storage is lowered and hence power run-out risk of the power storage becomes higher. Therefore, the power storage requested to carry out external power feed tends to excessively be high in power run-out risk. In this connection, according to the server, in selection by the selector of a power storage requested to carry out external power feed, the selector preferentially sequentially selects a power storage lower in power run-out risk and hence excessively high power run-out risk of the power storage is suppressed. 
     When the scheduler makes a schedule for issuing a request for suppressing external charging or carrying out external power feed, the scheduler may make the schedule such that a power storage lower in power run-out risk among the selected power storages starts earlier the request for suppressing external charging or carrying out external power feed. 
     In the server, in making the schedule for issuing a request for suppressing external charging, the schedule is made such that the request for suppressing external charging is started earlier in a power storage lower in power run-out risk. Therefore, a power storage high in power run-out risk can be lowered in power run-out risk by the time of start of the request. Excessively high power run-out risk of the power storage is thus suppressed. 
     In the server, in making the schedule for issuing a request for carrying out external power feed, the schedule is made such that the request for carrying out external power feed is started earlier in a power storage lower in power run-out risk. Therefore, a power storage high in power run-out risk can be lowered in power run-out risk by the time of start of the request. Excessively high power run-out risk of the power storage is thus suppressed. 
     When the selector selects a power storage requested to promote external charging by the request processor, the selector may preferentially sequentially select the power storage higher in power run-out risk. 
     In the server, in selection by the selector of a power storage requested to promote external charging, the selector preferentially sequentially selects a power storage higher in power run-out risk. Therefore, the power storage high in power run-out risk can be lowered in power run-out risk by carrying out external charging. Excessively high power run-out risk of the power storage is thus suppressed. 
     When the scheduler makes a schedule for issuing a request for promoting external charging, the scheduler may make the schedule such that a power storage higher in power run-out risk among the selected power storages starts earlier the request for promoting external charging. 
     In the server, in making the schedule for issuing a request for promoting external charging, the schedule is made such that the request for promoting external charging is started earlier in a power storage higher in power run-out risk. Therefore, by carrying out external charging early based on the request, the power storage high in power run-out risk can be lowered in power run-out risk early. Excessively high power run-out risk of the power storage is thus suppressed. 
     The plurality of power storages may be mounted on a plurality of mobile bodies, respectively. Any server described above may include a first estimator that estimates the power run-out risk for each mobile body based on at least one of long-distance travel capability, charging capability, a current position, a next travel distance, next departure time, a next travel route, and remaining energy for traveling for each mobile body. 
     With the first estimator, power run-out risk of the mobile body can more readily and appropriately be estimated. 
     A power management system according to a second point of view of the present disclosure includes any server described above and a plurality of mobile bodies. The plurality of power storages described previously are mounted on the plurality of mobile bodies, respectively. Each of the plurality of mobile bodies in the power management system includes a second estimator that estimates the power run-out risk of each of the plurality of mobile bodies based on at least one of long-distance travel capability, charging capability, a current position, a next travel distance, next departure time, a next travel route, and remaining energy for traveling of the mobile body. Each of the plurality of mobile bodies transmits the power run-out risk of the mobile body estimated by the second estimator to the server. 
     With the second estimator, power run-out risk of the mobile body can more readily and appropriately be estimated. 
     A mobile body lower in long-distance travel capability is higher in power run-out risk. Long-distance travel capability can broadly be categorized into a travelable distance in a full energy state and a rate of energy consumption (for example, electric power consumption or fuel efficiency) by traveling. 
     A mobile body longer in travelable distance in the full energy state is higher in long-distance travel capability. The full energy state means a state that the mobile body holds energy for traveling up to its limit. In general, a plug-in hybrid vehicle (PHV) that can travel with both of electricity and fuel is longer in travelable distance in the full energy state and higher in long-distance travel capability than an electric vehicle (EV) that travels only with electricity. As the power storage deteriorates, an amount of electricity stored in the power storage decreases. As the power storage included in the mobile body deteriorates, the travelable distance in the full energy state of the mobile body becomes shorter and hence long-distance travel capability of the mobile body becomes lower. 
     A mobile body lower in rate of energy consumption by traveling is higher in long-distance travel capability. In other words, a mobile body better in electric power consumption is higher in long-distance travel capability. The mobile body better in electric power consumption is smaller in amount of power consumption per unit travel distance. As the power storage deteriorates, an internal resistance of the power storage tends to increase. As the internal resistance of the power storage included in the mobile body increases, Joule loss increases and hence electric power consumption of the mobile body becomes poor. As the mobile body is heavier, energy required for traveling is higher and hence the rate of energy consumption by travel is higher. 
     As a mobile body is lower in charging capability, power run-out risk thereof becomes higher. For example, a mobile body including a charger adapted to both of alternating-current (AC) charging and direct-current (DC) charging is higher in charging capability than a mobile body including a charger adapted only to AC charging. A mobile body higher in charging power output from the charger to the power storage is higher in charging capability. As charging power is higher, a time period required for charging is shorter and power run-out risk is lower. 
     Power run-out risk of a mobile body may be varied also depending on a current position of the mobile body (and an environment around the mobile body). For example, when there are fewer charging facilities available for a mobile body in an area around the mobile body, power run-out risk is higher. When a charging facility available for a mobile body is provided in a house of a user of the mobile body, power run-out risk of the mobile body is lower while the mobile body is located in or around the house. 
     As a next travel distance is longer, power run-out risk is higher. As next departure time is earlier, power run-out risk is higher. The server may predict the next departure time for each mobile body based on history data 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). 
     As there are more slopes on a next travel route, power run-out risk is higher. When a mobile body flies, power run-out risk is higher in an air passage where it receives head wind. A user can set a next travel route, for example, with a well-known navigation system. The user can transmit the next travel route to the server with any communication equipment (for example, communication equipment mounted on the mobile body). 
     A mobile body less in remaining energy for traveling is higher in power run-out risk. Remaining energy for traveling refers to energy for traveling held in the mobile body. For example, in a case of an EV, remaining energy for traveling refers to an amount of stored power in a power storage, and in a case of a PHV, it refers to an amount of fuel in a fuel tank and an amount of stored power in a power storage. 
     As the first estimator is mounted on the server, the server can estimate power run-out risk for each mobile body based on information (that is, information indicating at least one of long-distance travel capability, charging capability, a current position, a next travel distance, next departure time, a next travel route, and remaining energy for traveling) received from each mobile body. The server can use the information received from each mobile body also for another purpose. For example, the server may carry out at least one of selection of a mobile body and making of a schedule described previously based on information received from each mobile body. 
     As the second estimator is mounted on each mobile body, each mobile body can estimate power run-out risk thereof based on the information (that is, information indicating at least one of long-distance travel capability, charging capability, a current position, a next travel distance, next departure time, a next travel route, and remaining energy for traveling) on the mobile body. Each mobile body can use the estimated power run-out risk also for another purpose. For example, when estimated power run-out risk exceeds a prescribed level, each mobile body may notify a user that power run-out risk is high. 
     Information (for example, power run-out risk) held by each mobile body may be sent from each mobile body directly to the server or from each mobile body to the server via another apparatus. 
     A server according to a third point of view of the present disclosure is usable 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 plurality of power storages are mounted on a plurality of mobile bodies, respectively. 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 promote external charging, suppress external charging, or carry out external power feed in accordance with the made schedule. The server obtains information on at least one of long-distance travel capability, charging capability, a current position, a next travel distance, next departure time, a next travel route, and remaining energy for traveling for each mobile body and carries out at least one of selection of the power storage and making of the schedule in accordance with a type of a request (that is, any of promotion of external charging, suppression of external charging, and external power feed) based on the obtained information. 
     According to the server, in requesting the user of the power storage to regulate supply and demand of electric power, compromise of convenience of the user of the power storage due to regulation of supply and demand of electric power can be suppressed. 
     A power management system according to a fourth point of view of the present disclosure includes any server described above and a plurality of vehicles. The plurality of power storages described previously are mounted on the plurality of vehicles, respectively. The power management system further includes a plurality of power facilities electrically connectable to the plurality of vehicles, respectively, and a power grid that supplies electric power to each of the plurality of power facilities. The request processor transmits a signal that requests a user of the vehicle to promote external charging, suppress external charging, or carry out 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 common to vehicles 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 and a server included in the power management system according to the embodiment of the present disclosure. 
         FIG. 5  is a diagram showing information used for estimating power run-out risk in the power management system according to the embodiment of the present disclosure. 
         FIG. 6  is a radar chart used for estimating power run-out risk in the power management system accenting to the embodiment of the present disclosure. 
         FIG. 7  is a flowchart showing processing performed by a 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. 8  is a diagram for illustrating selection of a DR vehicle made in the processing shown in  FIG. 7 . 
         FIG. 9  is a diagram for illustrating making of a charging schedule in the processing shown in  FIG. 7 . 
         FIG. 10  is a diagram for illustrating making of a charging suppression schedule in the processing shown in  FIG. 7 . 
         FIG. 11  is a diagram for illustrating making of a power feed schedule in the processing shown in  FIG. 7 . 
         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 showing a plurality of vehicles each incorporating an estimator in a modification. 
         FIG. 15  is a flowchart showing vehicle control based on power run-out risk in a modification. 
         FIG. 16  is a diagram for illustrating a modification of the estimator. 
     
    
    
     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 and a plurality of pieces of EVSE. EVSE means electric vehicle supply equipment. In this embodiment, the power management system includes an EV (that is, an electric vehicle that can travel with electric power stored in a powder storage) and a PHV (that is, a plug-in hybrid vehicle that can travel with both of electric power stored in a power storage and engine output). The power management system includes AC type EVSE (that is, a normal charger) and DC type EVSE (for example, a quick charger). Each of the plurality of vehicles included in the power management system is denoted as a “vehicle  50 ” below and each of the 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. 
       FIG. 1  is a diagram showing a configuration common among vehicles  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 . 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 AC type EVSE. EVSE  40  shown in  FIG. 1  is AC type EVSE. 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 . Vehicle  50  may include an inlet and a charger-discharger (neither of which is shown) adapted to DC type EVSE in addition to inlet  110  and charger-discharger  120 . 
     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  49  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 AC power received at inlet  110  into DC power suitable for charging of battery  130  and outputs DC 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 DC power supplied from battery  130  into AC power suitable for external power feed and outputs AC 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 nonvolatile 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 of 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. 
     Travel driving unit  140  of the PHV further includes an engine (an internal combustion engine), a fuel tank, and a fuel pump (none of which is shown). The fuel tank is provided with a fuel sensor (not shown) that detects a remaining amount of fuel and outputs the amount to ECU  150 . Fuel (for example, gasoline) in the fuel tank is supplied to the engine by the fuel pump and converted to motive power in the engine. Motive power output from the engine rotates drive wheel W. The PHV may include a generator that generates electric power with motive power output from the engine. The MG described previously may generate electric power with motive power output from the engine. Electric power generated by the engine may be stored in battery  130  or used for traveling of the PHV. 
     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 (I/F). 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  (winch 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 datacenter  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 . A schedule set in a scheduler application or a wake-up application installed in portable terminal  80  may automatically be transmitted to data center  70 . 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 a drive plan of a POV (for example, time of departure from home, a destination, and arrival time) 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 a 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. 7  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 or 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 . 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  11  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 back fed from vehicle  50  through charging cable  42  and power supply circuit  41  to power grid PG. Power supply circuit  11  converts electric power supplied from power grid PG into electric power suitable tor 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  40 I, 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. In this embodiment, vehicle  50 A is a PHV and each of vehicles  50 B to  50 D is an EV. Each of pieces of EVSE  40 A to  40 I 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  40 I. 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  40 I. 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 contribute to regulation of supply and demand of electric power by meeting the request from server  30 . As power run-out risk of vehicle  50  becomes higher due to regulation of supply and demand of electric power, however, convenience of the user of vehicle  50  may be compromised. 
     With a configuration which will be described below, the power management system (VGI system  1 ) according to this embodiment suppresses excessively high power run-out risk of vehicle  50  due to regulation of supply and demand of electric power (and compromise of convenience of the user of vehicle  50 ) when server  30  requests the user of vehicle  50  to regulate supply and demand of electric power.  FIG. 4  is a diagram showing a detailed configuration of ECU  150  of vehicle  50  and server  30 . 
     Referring to  FIG. 4 , 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 , and a request processor  305 . 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 . Storage  153  stores in advance information representing specifications (for example, travel capability and charging capability) of vehicle  50 . Information representing the specifications of vehicle  50  is also referred to as “spec information” below. Information manager  501  transmits spec information to server  30  at the time of registration of vehicle  50  in server  30  or in response to a request from server  30 . Information on vehicle  50  transmitted from vehicle  50  to server  30  is also referred to as “vehicle information” below. Information manager  301  of server  30  has storage  32  store vehicle information received from vehicle  50  in association with a vehicle ID of vehicle  50 . 
     Estimator  302  of server  30  estimates power run-out risk for each vehicle based on long-distance travel capability, charging capability, a next travel distance, next departure time, and remaining energy for traveling (which is also simply referred to as “remaining energy” below) for each vehicle. Estimator  302  according to this embodiment corresponds to an exemplary “first estimator” according to the present disclosure. Estimation of power run-out risk of vehicle  50  by estimator  302  of server  30  will be described below with reference to  FIGS. 5 and 6 . 
       FIG. 5  is a diagram showing information used for estimating power run-out risk. Referring to  FIG. 5 , estimator  302  estimates power run-out risk of vehicle  50  based on a next travel distance (which is also referred to as “Y 1 ” below) of vehicle  50 , next departure time (which is also referred to as “Y 2 ” below) of vehicle  50 , remaining energy (which is also referred to as “Y 3 ” below) of vehicle  50 , charging power (which is also referred to as “Y 4 ” below) for battery  130 , PHV/EV information (which is also referred to as “Y 5 ” below), charging equipment information (which is also referred to as “Y 6 ” below), and a degree of deterioration (which is also referred to as “Y 7 ” below) of battery  130 . 
     Y 1  may represent a next travel distance obtained from a user or a next travel distance estimated by server  30 . Server  30  can obtain Y 1  based on information (for example, a drive plan of a PVO or a drive plan of a MaaS vehicle) received from a user. Server  30  can also estimate Y 1  from vehicle information received from vehicle  50 . Server  30  may estimate Y 1  from a travel distance or a destination in the past (history data). Server  30  may predict a next travel distance based on learning with history data. Artificial intelligence (AI) may be used tor learning. 
     Y 2  may represent next departure time obtained from a user or next departure time estimated by server  30 . Server  30  can obtain Y 2  based on information received from a user (for example, a drive plan of a PVO or a drive plan of a MaaS vehicle). Server  30  can also estimate Y 2  from vehicle information received from vehicle  50 . Server  30  may estimate Y 2  from a charging location, arrival time, and departure time in the past (history data). Arrival time refers to lime when vehicle  50  arrives at a charging location. Departure time refers to time when vehicle  50  leaves a charging location. Server  30  may predict next departure lime based on learning with history data. Artificial intelligence (AI) may be used for learning. 
     Y 3  represents an amount of energy resource held by vehicle  50  for driving drive wheel W by means of travel driving unit  140 . In a case of an EV, an amount of stored power in battery  130  corresponds to Y 3 . An amount of stored power in battery  130  corresponds to an amount of electricity that can be supplied to an MG for travel driving. In a case of a PHV, a value of the sum of an amount of stored power in battery  130  and an amount of fuel in a fuel tank as being converted to travel driving energy corresponds to Y 3 . 
     Y 4  represents charging power for battery  130  (that is, electric power output from charger-discharger  120  to battery  130  in charging of battery  130 ). When charging power for battery  130  is variable, maximum charging power corresponds to Y 4 . Y 4  corresponds to exemplary “charging capability.” Server  30  can receive Y 4  from vehicle  50 . In this embodiment, vehicle information (more specifically, spec information) includes Y 4 . 
     Y 5  represents information on whether vehicle  50  falls under an EV or a PHV. A PHV is longer in travelable distance in the fully energy state than an EV. Therefore, the PHV is higher in long-distance travel capability than the EV. Y 5  corresponds to exemplary “long-distance travel capability.” Server  30  can receive Y 5  from vehicle  50 . In this embodiment, vehicle information (more specifically, spec information) includes Y 5 . 
     Vehicle  50  according to this embodiment includes inlet  110  and charger-discharger  120  adapted to AC type EVSE as standard equipment. An inlet and a charger-discharger adapted to DC type EVSE can be added to vehicle  50 . The inlet and the charger-discharger adapted to DC type EVSE fall under optional charging equipment. Whether or not to mount optional charging equipment on vehicle  50  can be selected by a user of vehicle  50 . Y 6  represents information on whether or not optional charging equipment is mounted on vehicle  50 . Vehicle  50  without optional charging equipment can carry out external charging only with AC type EVSE. Vehicle  50  incorporating optional charging equipment can carry out external charging with both of AC type EVSE and DC type EVSE. Y 6  corresponds to exemplary “charging capability.” Server  30  can receive Y 6  from vehicle  50 . In this embodiment, vehicle information (more specifically, spec information) includes Y 6 . 
     Y 7  represents information on a degree of deterioration of battery  130 . Y 7  may represent a capacity retention of battery  130 . The capacity retention of battery  130  is an expression in percentage of a ratio of a current capacity to an initial capacity. The initial capacity refers to a capacity of battery  130  in an initial state. The current capacity refers to a capacity of battery  130  at the current time point. The degree of deterioration of battery  130  is lower as the capacity retention of battery  130  is higher. Y 7 , however is not limited to represent the capacity retention of battery  130  but it may represent an internal resistance of battery  130 . As the internal resistance of battery  130  is higher, the degree of deterioration of battery  130  is higher. Server  30  can estimate Y 7  from vehicle information received from vehicle  50 . Server  30  can estimate the degree of deterioration of battery  130  with a known method (for example, an AC impedance method, an AC internal resistance method, a direct charging and discharging measurement method, a discharge curve differentiation method, a charging curve analysis method, or an estimation method based on a charging and discharging history). 
       FIG. 6  shows a radar chart used for estimating power run-out risk. Y 1  to Y 7  in  FIG. 6  are the same as Y 1  to Y 7  shown in  FIG. 5 . Referring to  FIG. 6 , a radar chart M shows power run-out risk of vehicle  50 A ( FIG. 3 ) and power run-out risk of vehicle  50 B ( FIG. 3 ) in contrast with each other. A center Y 0  indicates the origin of radar chart M. As a degree of increase in power run-out risk is higher, line data of items from Y 1  to Y 7  is plotted at a position more distant from center Y 0  (on an outer side). More specifically, as the next travel distance (Y 1 ) of vehicle  50  is longer, power run-out risk is higher. Therefore, the line data of Y 1  is plotted on the further outer side as the next travel distance of vehicle  50  is longer. As next departure time (Y 2 ) of vehicle  50  is earlier, power run-out risk is higher. Therefore, the line data of Y 2  is plotted on the further outer side as next departure time of vehicle  50  is earlier. As remaining energy (Y 3 ) of vehicle  50  is less, power run-out risk is higher. Therefore, the line data of Y 3  is plotted on the further outer side as remaining energy of vehicle  50  is less. As charging power (Y 4 ) for battery  130  is higher, time required for charging is shorter and power run-out risk is lower. Therefore, the line data of Y 4  is plotted on the further outer side as charging power for battery  130  is lower. Since the PHV is longer than the EV in travelable distance in the full energy state, power run-out risk is lower. Therefore, the line data of PHV/EV information (Y 5 ) is plotted on the further outer side for the EV as compared with the PHV. Vehicle  50  adapted to both of AC charging and DC charging is lower in power run-cut risk than vehicle  50  adapted only to AC charging. Therefore, the line data of charging equipment information (Y 6 ) is plotted on the further outer side in the case “without optional charging equipment” as compared with the case “with optional charging equipment.” As the degree of deterioration (Y 7 ) of battery  130  is higher, long-distance travel capability of vehicle  50  is lower and power run-out risk is higher. Therefore, the line data of Y 7  is plotted on the further outer side as the degree of deterioration of battery  130  is higher. 
     Lines L 1  and L 2  show power run-out risks of vehicles  50 A and  50 B, respectively. Areas on the inner side of lines L 1  and L 2  correspond to power run-out risks of vehicles  50 A and  50 B, respectively. As the area is larger, power run-out risk is higher. Radar chart M shows that vehicle  50 B is higher in power run-out risk than vehicle  50 A. 
     Any scale (and weight for each item) for Y 1  to Y 7  in radar chart M can be set by a user. The user may set the scale for Y 1  to Y 7  based on relation between power run-out risk and each of Y 1  to Y 7  obtained through experiments or simulation. A method of estimating power run-out risk is not limited to the method using the radar chart, and power run-out risk may be calculated based on Y 1  to Y 7  by using a mathematical expression obtained by statistical learning with big data (for example, an expression that expresses relation between Y 1  to Y 7  and power run-out risk). 
     Referring again to  FIG. 4 , estimator  302  of server  30  estimates power run-out risk for each vehicle  50  and has storage  32  store the estimated power run-out risk in association with a vehicle ID. Power run-out information representing power run-out risk of each vehicle  50  is thus stored in storage  32 . Estimator  302  estimates power run-out risk and updates power run-out information at any time based on most recent vehicle information. Estimator  302  may have storage  32  store real-time power run-out risk of each vehicle  50  by highly frequently updating power run-out information. 
     Though details will be described later, 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 . 
     When information manager  501  receives the DR signal from server  30 , the DR signal is stored in storage  153 . The user of vehicle  50  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. 
     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 . 
       FIG. 7  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. 7  together with  FIGS. 1 to 4 , 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, promotion of external charging, suppression of external charging, or 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. 
     Selector  303  selects a DR vehicle based on the request contents obtained in S 11  and power run-out information ( FIG. 4 ) in storage  32 . 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.  FIG. 8  is a diagram for illustrating selection of a DR vehicle. 
     Referring to  FIG. 8 , in this embodiment, a type of electric power regulation indicated in the request contents falls under any of suppression of external charging, execution of external power feed, and promotion of external charging. 
     When vehicle  50  is requested to suppress external charging, lowering in power run-out risk thereof by external charging is restricted, and it becomes difficult for the vehicle to prevent power run-out risk from becoming excessively high. Then, when the type of requested electric power regulation falls under suppression of external charging, selector  303  preferentially sequentially selects vehicle  50  lower in power run-out risk. Excessively high power run-out risk of vehicle  50  is thus suppressed. 
     As vehicle  50  carries out external power feed, the SOC of battery  130  is lowered and power run-out risk of vehicle  50  becomes higher. When the type of requested electric power regulation falls under execution of external power feed, selector  303  then preferentially sequentially selects vehicle  50  lower in power run-out risk. Excessively high power run-out risk of vehicle  50  is thus suppressed. 
     When the type of requested electric power regulation falls under promotion of external charging, selector  303  preferentially sequentially selects vehicle  50  higher in power run-out risk. Therefore, vehicle  50  high in power run-out risk can be lowered in power run-out risk by carrying out external charging. Excessively high power run-out risk of vehicle  50  is thus suppressed. 
     When there are a large number of vehicles  50  equal in power run-out risk and a prescribed number of DR vehicles cannot be selected only based on the power run-out risk, selector  303  may narrow down candidates for the DR vehicle based on the power run-out risk and thereafter select the DR vehicles based on an arbitrary reference (or randomly) from among a plurality of vehicles  50  equal in power run-out risk. 
     Referring again to  FIG. 7  together with  FIGS. 1 to 4 , after processing in S 12 , the process proceeds to S 13 . 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 S 11  indicate a request for promotion of external charging, scheduler  304  makes a charging schedule indicating time to start and quit external charging. When the request contents obtained in S 11  indicate a request for suppression of external charging, scheduler  304  makes a charging suppression schedule indicating time to start and quit charging restriction. When the request contents obtained in S 11  indicate a request for carrying out external power feed, scheduler  304  makes a power feed schedule indicating time to start and quit external power feed. Scheduler  304  makes a schedule for each DR vehicle based on the request contents obtained in S 11  and the power run-out information ( FIG. 4 ) in storage  32 . 
     Making of a schedule for vehicles  50 A to  50 C shown in  FIG. 3  will be described below with reference to  FIGS. 9 to 11 . Vehicles  50 A to  50 C are higher in power run-out risk in the order of vehicle  50 B, vehicle  50 C, and vehicle  50 A. 
       FIG. 9  is a diagram for illustrating making of a charging schedule. Referring to  FIG. 9  together with  FIGS. 1 to 4 , scheduler  304  makes a charging schedule such that a request is started earlier in a DR vehicle higher in power run-out risk among DR vehicles selected in S 12 . For example, when vehicles  50 A to  50 C are selected in S 12 , scheduler  304  makes charging schedules Sc 11  to Sc 13  for vehicles  50 A to  50 C such that a request is started in the order of charging schedule Sc 11  for vehicle  50 B (high in power run-out risk), charging schedule Sc 12  for vehicle  50 C (intermediate in power un-out risk), and charging schedule Sc 13  for vehicle  50 A (low in power run-out risk). By carrying out external charging early based on the request, vehicle  50 B high in power run-out risk can thus be lowered in power run-out risk early. Excessively high power run-out risk of each DR vehicle is thus suppressed. 
       FIG. 10  is a diagram for illustrating making of a charging suppression schedule. Referring to  FIG. 10  together with  FIGS. 1 to 4 , scheduler  304  makes a charging suppression schedule such that a request is started earlier in a DR vehicle lower in power run-out risk among DR vehicles selected in S 12 . For example, when vehicles  50 A to  50 C are selected in S 12 , scheduler  304  makes charging suppression schedules Sc 21  to Sc 23  for vehicles  50 A to  50 C such that the request is started in the order of charging suppression schedule Sc 21  for vehicle  50 A (low in power run-out risk), charging suppression schedule Sc 22  for vehicle  50 C (intermediate in power run-out risk), and charging suppression schedule Sc 23  for vehicle  50 B (high in power run-out risk). Vehicle  50 B high in power run-out risk can thus be lowered in power run out risk during a DR grace period (a period by the time of start of the request). Examples of a method of lowering power ran-out risk during the DR grace period include charging battery  130  with a power supply (for example, a spare power storage) other than power grid PG, refueling the PHV, and changing a next travel schedule. The charging suppression schedule made as above suppresses excessively high power run-out risk of each DR vehicle. 
       FIG. 11  is a diagram for illustrating making of a power feed schedule. Referring to  FIG. 11  together with  FIGS. 1 to 4 , scheduler  304  makes a power feed schedule such that a request is started earlier in a DR vehicle lower in power run-out risk among DR vehicles selected in S 12 . For example, when vehicles  50 A to  50 C are selected in S 12 , scheduler  304  makes power feed schedules Sc 31  to Sc 33  for vehicles  50 A to  50 C such that the request is started in the order of power feed schedule Sc 31  for vehicle  50 A (low in power run-out risk), power feed schedule Sc 32  for vehicle  50 C (intermediate in power run-out risk), and power feed schedule Sc 33  for vehicle  50 B (high in power run-out risk). Vehicle  50 B high in power run-out risk can thus be lowered in power run-out risk during the DR grace period. Excessively high power run-out risk of each DR vehicle is thus suppressed. 
     Referring again to  FIG. 7  together with  FIGS. 1 to 4 , 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 . 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 that any of promotion of external charging, suppression of external charging, and external power feed is earned out in accordance with the schedule included in each DR signal. 
     During a period other than the DR period, ECU  150  carries out immediate charging and timer-programmed charging based on an instruction from a user (for example, a prescribed operation). Immediate charging refers to external charging started immediately after completion of preparation for external charging in vehicle  50 . Timer-programmed charging refers to external charging carried out in accordance with a schedule programmed in ECU  150 . During the DR period, however, ECU  150  carries out charging and discharging control of battery  130  with priority being placed on a command from server  30  over the timer-programmed schedule of charging. When ECU  150  receives a charging start command from server  30  before time to start timer-programmed charging, it starts charging of battery  130  in accordance with the command from server  30 . 
     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 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. 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 S 58 , 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 50  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 power run-out information indicating power run-out risk for each vehicle and makes selection (S 12  in  FIG. 7 ) of a DR vehicle and makes a schedule (S 13  in  FIG. 7 ) based on the obtained power run-out information. For a request that raises power run-out risk, in selection of a DR vehicle, server  30  makes vehicle  50  high in power run-out risk less likely to be selected. In making a schedule for vehicle  50  high in power run-out risk, server  30  suppresses increase in power run-out risk by adjusting time to start the request. In requesting a user of vehicle  50  including battery  130  to regulate supply and demand of electric power, the power management system can suppress excessively high power run-out risk of vehicle  50  (and compromise of convenience of the user of vehicle  50 ) caused by regulation of supply and demand of electric power. 
     Though power run-out information is used for both of selection of a DR vehicle (S 12  in  FIG. 7 ) and making of a schedule (S 13  in  FIG. 7 ) in the embodiment, the power run-out 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 power run-out information. When vehicle  50  is newly electrically connected to power grid PG after DR is started, server  30  may add newly connected vehicle  50  to candidates for the DR vehicle and select again the DR vehicle based on power run-out information. 
     In the embodiment, the estimator (estimator  302 ) that estimates power run-out risk of vehicle  50  is mounted on server  30 . Without being limited as such, each vehicle  50  may include an estimator and the estimator may estimate power run-out risk of vehicle  50   FIG. 14  is a diagram showing a plurality of vehicles  50  each incorporating an estimator. In  FIG. 14 , each of ECUs  150 A to  150 C functions as the estimator. Each of ECUs  150 A to  150 C corresponds to an exemplary “second estimator” according to the present disclosure. 
     Referring to  FIG. 14 , vehicles  50 A to  50 C shown in  FIG. 3  include ECUs  150 A to  150 C, respectively. ECUs  150 A to  150 C estimate power run-out risks A to C of vehicles  50 A to  50 C, respectively. The method of estimating power run-out risk is the same as in the embodiment described previously (see  FIGS. 5 and 6 ). Vehicles  50 A to  50 C transmit power run-out risks estimated by ECUs  150 A to  150 C to server  30 . Server  30  can obtain power run-out risk for each vehicle from each vehicle  50 . Information thus transmitted from each vehicle  50  to server  30  corresponds to power run-out information. Server  30  can carry out at least one of selection of a DR vehicle (S 12  in  FIG. 7 ) and making of a schedule (S 13  in  FIG. 7 ) based on power run-out information. 
     Each of vehicles  50 A to  50 C shown in  FIG. 14  may use power run-out risk estimated as above for vehicle control.  FIG. 15  is a flowchart showing exemplary vehicle control based on power run-out risk. Processing shown in this flowchart is repeatedly performed in each vehicle  50  including the estimator. 
     Referring to  FIG. 15  together with  FIGS. 1 and 2 , in S 71 , ECU  150  determines whether or not estimated power run-out risk exceeds a prescribed level. While determination as NO is made in S 71  (power run-out risk does not exceed the prescribed level), ECU  150  repeatedly makes determination, and when determination as YES is made in S 71  (power run-out risk exceeds the prescribed level), the ECU performs prescribed processing in S 72 . In S 72 , ECU  150  may notify a user of high power run-out risk. ECU  150  may instruct any of notification apparatus  170  and portable terminal  80  to give a notification. In S 72 , ECU  150  may control storage  153  to record high power run-out risk together with current time. In S 72 , ECU  150  may restrict a travel mode of vehicle  50  to a mode in which electric power consumption is prioritized over travel power. 
     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 ). 
     It is not essential that the inlet and the charger-discharger adapted to the DC type EVSE are optional charging equipment for vehicle  50  The power management system may include a vehicle including a DC type charger but not including an AC type charger. Though the DC type charger is generally higher in charging power than the AC type charger, the DC type EVSE is less prevalent than the AC type EVSE. Server  30  may evaluate power run-out risk of each vehicle in consideration of a status of infrastructures for charging (for example, a rate of penetration of the DC type EVSE). 
     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 power management system is not limited to VGI system  1  shown in  FIGS. 2  and  3 . 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. 7 ). 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 dial 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). 
     The estimator adopted in the power management system may estimate power run-out risk of any mobile body. The estimator may be mounted on any of the server, the mobile body, and the portable terminal.  FIG. 16  is a diagram for illustrating a modification of the estimator. 
     Referring to  FIG. 16 , the estimator may estimate power run-out risk of a mobile body based on a next travel distance, next departure time, remaining energy for traveling, charging capability, long-distance travel capability, a current position, and a next travel route of the mobile body. Y 1  described previously corresponds to an exemplary “next travel distance.” Y 2  described previously corresponds to exemplary “next departure time.” Y 3  described previously corresponds to exemplary “remaining energy for traveling.” Y 4  and Y 6  described previously correspond to exemplary “charging capability.” Y 5  and Y 7  described previously correspond to exemplary “long-distance travel capability.” Since the next travel distance, next departure time, remaining energy for traveling, charging capability, and long-distance travel capability are adopted in the embodiment described previously, description will not be provided. 
     The estimator may estimate power run-out risk of the mobile body based on a current position and a next travel route of the mobile body. The estimator can obtain a current position of the mobile body, for example, with a sensor based on the GPS. A user may set the next travel route, for example, with a well-known navigation system. The estimator may obtain the next travel route from the navigation system. The estimator may estimate power run-out risk of a mobile body as being higher as there are fewer charging facilities available for the mobile body in an area around the mobile body. The estimator may estimate power run-out risk of the mobile body in consideration of a direction of wind, a gradient of a road, a state of a road surface, and congestion over the next travel route. 
     Though the estimator may estimate power run-out risk based on only one of a next travel distance, next departure time, remaining energy for traveling, charging capability, long-distance travel capability, a current position, and a next travel route of the mobile body, the estimator more readily estimates power run-out risk at high accuracy based on three or more of them. In particular, the estimator more readily estimates power run-out risk at high accuracy based on next departure time, remaining energy for traveling, and long-distance travel capability. 
     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.