Patent Publication Number: US-8988042-B2

Title: Vehicle, charging system and control method for vehicle

Description:
TECHNICAL FIELD 
     The present invention relates to a vehicle, a charging system and a control method for the vehicle, and more particularly to charging control for the vehicle in which a power storage device mounted thereon can be charged with electric power provided from an external power supply. 
     BACKGROUND ART 
     In recent years, a vehicle that has a power storage device (e.g., a secondary battery, a capacitor and the like) mounted thereon and runs using driving force generated from electric power stored in the power storage device has received attention as an environmentally-friendly vehicle. This vehicle includes, for example, an electric vehicle, a hybrid vehicle, a fuel cell vehicle and the like. There has been proposed a technique of charging the power storage device mounted on this vehicle by a commercial power supply having high power generation efficiency. 
     Similarly to the electric vehicle, as for the hybrid vehicle, there has been known a vehicle in which charging (hereinafter, also simply referred to as “external charging”) of a vehicle-mounted power storage device by a power supply external to the vehicle (hereinafter, also simply referred to as “external power supply”) is possible. For example, there has been known a so-called “plug-in hybrid vehicle” in which the power storage device can be charged from a power supply in an ordinary household by connecting an outlet provided at a house and a charging port provided at the vehicle through a charging cable. It can be expected that this leads to enhancement of the fuel consumption efficiency of the hybrid vehicle. 
     Japanese Patent Laying-Open No. 2009-033265 (PTL 1) discloses such a configuration that, in a vehicle capable of external charging, information is transmitted between the vehicle and an external power supply as well as between the vehicle and another vehicle via a charging port by Power Line Communication (PLC). 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: Japanese Patent Laying-Open No. 2009-033265 
         PTL 2: WO 2011/077505 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In external charging, a signal is received and transmitted between the vehicle and the charging cable or between the vehicle and the external power supply, and information such as a capacity of charging power that can be transmitted from the external power supply and a rated current of the charging cable is transmitted to the vehicle. Based on the transmitted information, the vehicle starts/stops charging and controls the charging power. 
     Such transmission of the information may be implemented using a pilot signal provided from the charging cable or the external power supply. 
     In recent years, there has been developed a technique like smart grid of not only charging a vehicle-mounted power storage device using a household power supply (external power supply) but also supplying electric power stored in the vehicle to a household when necessary. In such a case, supply/interruption of electric power and control over supplied electric power from the household side to the vehicle side are necessary, and use of the PLC communication that does not require addition of a special wiring has been under consideration. 
     In some types of the external power supply and the charging cable, however, the PLC communication cannot be appropriately established when a power interruption relay included in the external power supply and the charging cable interrupts a power transmission path. Further, the fixed and the same external power supply and charging cable are not always connected to the vehicle. Therefore, in the vehicle, it must be determined whether communication with the external power supply and the charging cable is established using the pilot signal or using the PLC communication. 
     The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to, in a vehicle capable of external charging, achieve reliable transmission of information between the vehicle and a connected external power supply or power cable. 
     Solution to Problem 
     In a vehicle according to the present invention, a power storage device mounted thereon can be charged with electric power transmitted from an external power supply device via a power cable. The vehicle includes: an inlet to which the power cable is connected; a PLC communication unit configured to be capable of establishing power line communication with the external power supply device via a power line in the power cable; and a control device for controlling a charging operation of the power storage device. The power cable or the external power supply device includes a switching device for switching between supply and interruption of the electric power from the external power supply device to the vehicle. The control device starts transmission of a signal from the PLC communication unit to the external power supply device in response to connection of the power cable to the inlet, and when a transmission signal from the external power supply device to the PLC communication unit is not received, the control device switches the switching device to a state in which the supply of the electric power from the external power supply device to the vehicle is possible, and thereafter, retransmits the signal from the PLC communication unit to the external power supply device. 
     Preferably, when the power cable is connected to the inlet, the control device changes a potential of a pilot signal from the switching device to a first potential, and thereafter, starts transmission by the PLC communication unit. 
     Preferably, the transmission signal is a response from the external power supply device to transmission of the signal from the PLC communication unit to the external power supply device. When the transmission signal is received, the control device changes the potential of the pilot signal to a second potential lower than the first potential to switch the switching device to the state in which the supply of the electric power from the external power supply device to the vehicle is possible, and performs the charging operation based on communication information from the external power supply device. 
     Preferably, the transmission signal is a response from the external power supply device to transmission of the signal from the PLC communication unit to the external power supply device. When the transmission signal is not received, the control device suspends transmission by the PLC communication unit, changes the potential of the pilot signal to a second potential lower than the first potential to switch the switching device to the state in which the supply of the electric power from the external power supply device to the vehicle is possible, and thereafter, executes retransmission by the PLC communication unit. 
     Preferably, when the response from the external power supply device to the signal retransmitted from the PLC communication unit is received, the control device performs the charging operation based on communication information from the external power supply device. 
     Preferably, when the response from the external power supply device to the signal retransmitted from the PLC communication unit is not received, the control device stops transmission by the PLC communication unit. 
     Preferably, when the response from the external power supply device to the signal retransmitted from the PLC communication unit is not received, the control device performs the charging operation based on an oscillation state of the pilot signal. 
     Preferably, when the response from the external power supply device to the signal retransmitted from the PLC communication unit is not received, the control device notifies a user that PLC communication cannot be established between the vehicle and the external power supply device. 
     Preferably, the vehicle is configured to be capable of supplying electric power from the power storage device to an external device connected to the external power supply device, via the inlet and the power cable. 
     Preferably, the PLC communication unit is configured to be capable of establishing power line communication with the external power supply device via the power line in the power cable. The control device performs a power feeding operation based on communication information from the external power supply device. 
     Preferably, the switching device includes: a relay for switching between electrical connection and disconnection between a power source in the external power supply device and the vehicle; and a signal generation unit for generating a pilot signal transmitted to the control device via a communication line included in the power cable and different from the power line. The signal generation unit causes the pilot signal to oscillate in response to a fact that a potential of the pilot signal attains a first potential. The relay is closed in response to a fact that the potential of the pilot signal attains a second potential lower than the first potential. 
     A charging system according to the present invention includes: a power cable; an external power supply device; and a vehicle in which a power storage device mounted thereon can be charged with electric power transmitted from the external power supply device via the power cable. The vehicle includes: an inlet to which the power cable is connected; a PLC communication unit configured to be capable of establishing power line communication with the external power supply device via a power line in the power cable; and a control device for controlling a charging operation of the power storage device. The power cable or the external power supply device includes a switching device for switching between supply and interruption of the electric power from the external power supply device to the vehicle. The control device starts transmission of a signal from the PLC communication unit to the external power supply device in response to connection of the power cable to the inlet, and when a transmission signal from the external power supply device to the PLC communication unit is not received, the control device switches the switching device to a state in which the supply of the electric power from the external power supply device to the vehicle is possible, and thereafter, retransmits the signal from the PLC communication unit to the external power supply device. 
     A control method for a vehicle according to the present invention is directed to a control method for a vehicle in which a power storage device mounted thereon can be charged with electric power transmitted from an external power supply device via a power cable. The vehicle includes: an inlet to which the power cable is connected; and a PLC communication unit configured to be capable of establishing power line communication with the external power supply device via a power line in the power cable. The power cable or the external power supply device includes a switching device for switching between supply and interruption of the electric power from the external power supply device to the vehicle. The control method includes the steps of: determining whether or not the power cable is connected to the inlet; starting transmission of a signal from the PLC communication unit to the external power supply device in response to connection of the power cable to the inlet; and when a transmission signal from the external power supply device to the PLC communication unit is not received, switching the switching device to a state in which the supply of the electric power from the external power supply device to the vehicle is possible, and thereafter, retransmitting the signal from the PLC communication unit to the external power supply device. 
     Advantageous Effects of Invention 
     According to the present invention, in the vehicle capable of external charging, reliable transmission of information can be achieved between the vehicle and the connected external power supply or power cable. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an overall block diagram of a charging system including a vehicle according to the present embodiment. 
         FIG. 2  is a block diagram for describing a charging operation in the charging system in  FIG. 1 . 
         FIG. 3  is an overall block diagram of a charging system when an external power supply is provided with a CCID function. 
         FIG. 4  is a block diagram for describing a charging operation in the charging system in  FIG. 3 . 
         FIG. 5  is a time chart of the charging operation in the charging system in  FIG. 3 . 
         FIG. 6  is a time chart of the charging operation in the charging system in  FIG. 1 . 
         FIG. 7  is a time chart of a charging operation when PLC communication is impossible. 
         FIG. 8  is a flowchart for describing a charging process executed by an ECU in the present embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described in detail hereinafter with reference to the drawings, in which the same or corresponding portions are denoted by the same reference characters and description thereof will not be repeated. 
     [Description of Charging System] 
       FIG. 1  is an overall block diagram of a charging system  10  including a vehicle  100  according to the present embodiment. Referring to  FIG. 1 , vehicle  100  includes a power storage device  110 , a system main relay (SMR)  115 , a PCU (Power Control Unit)  120  serving as a drive device, motor generators  130  and  135 , a motive power transmission gear  140 , a driving wheel  150 , an engine  160  serving as an internal combustion engine, and an ECU (Electronic Control Unit)  300  serving as a control device. PCU  120  includes a converter  121 , inverters  122  and  123 , and capacitors C 1  and C 2 . 
     Although a hybrid vehicle having motor generators  130  and  135  and engine  160  is described by way of example in the present embodiment, engine  160  is not an essential component. The present invention is also applicable to an electric vehicle or a fuel cell vehicle that does not have engine  160 . 
     Power storage device  110  is an electric power storage element configured to be rechargeable. Power storage device  110  is configured to include a power storage element such as, for example, a secondary battery including a lithium ion battery, a nickel-metal hydride battery, a lead storage battery or the like, or an electric double layer capacitor. 
     Power storage device  110  is connected to PCU  120  by power lines PL 1  and NL 1 . Power storage device  110  supplies electric power for generating driving force of vehicle  100  to PCU  120 . Power storage device  110  also stores electric power generated by motor generators  130  and  135 . The output of power storage device  110  is approximately 200 V, for example. 
     Power storage device  110  includes a voltage sensor and a current sensor that are not shown, and outputs a voltage VB and a current TB of power storage device  110  detected by these sensors to ECU  300 . 
     One relay included in SMR  115  is connected to a positive electrode end of power storage device  110  and power line PL 1  connected to PCU  120 , and the other relay is connected to a negative electrode end of power storage device  110  and power line NL 1 . Based on a control signal SE 1  provided from ECU  300 , SMR  115  switches between supply and interruption of electric power between power storage device  110  and PCU  120 . 
     Based on a control signal PWC provided from ECU  300 , converter  121  makes voltage conversion between power lines PL 1 , NL 1  and power lines PL 2 , NL 1 . 
     Inverters  122  and  123  are connected to power lines PL 2  and NL 1  in parallel. Based on control signals PWI 1  and PWI 2  provided from ECU  300 , inverters  122  and  123  convert DC electric power supplied from converter  121  into AC electric power and drive motor generators  130  and  135 , respectively. 
     Capacitor C 1  is provided between power lines PL 1  and NL 1 , and reduces voltage fluctuations between power lines PL 1  and NL 1 . Capacitor C 2  is provided between power lines PL 2  and NL 1 , and reduces voltage fluctuations between power lines PL 2  and NL 1 . 
     Motor generators  130  and  135  are each an AC rotating electric machine, and for example a permanent magnet-type synchronous motor including a rotor having a permanent magnet embedded therein. 
     Output torque of motor generators  130  and  135  is transmitted to driving wheel  150  via motive power transmission gear  140  configured to include a reducer and a power split device, and causes vehicle  100  to run. During the regenerative braking operation of vehicle  100 , motor generators  130  and  135  can generate electric power using rotational force of driving wheel  150 . The generated electric power is then converted by PCU  120  into charging power of power storage device  110 . 
     Further, motor generators  130  and  135  are coupled to engine  160  via motive power transmission gear  140 . Motor generators  130  and  135  as well as engine  160  are cooperatively operated by ECU  300  so as to generate necessary vehicle driving force. Furthermore, motor generators  130  and  135  can generate electric power by rotation of engine  160 , and power storage device  110  can be charged using this generated electric power. It is to be noted that in the present embodiment, motor generator  135  is used entirely as a motor for driving wheel  150 , and motor generator  130  is used entirely as a generator driven by engine  160 . 
     Although  FIG. 1  shows by way of example the configuration in which two motor generators are provided, the number of motor generators is not limited thereto. One motor generator or more than two motor generators may be provided. 
     As a configuration for charging power storage device  110  with electric power provided from an AC power source  510  in external power supply device  500 , vehicle  100  includes a power conversion device  200 , a charging relay CHR  210 , an inlet  220  serving as a connecting unit, and a PLC communication unit  230  for the PLC communication. 
     A connector  410  of a power cable  400  is connected to inlet  220 . The electric power provided from external power supply device  500  is transmitted to vehicle  100  via power cable  400 . 
     In addition to connector  410 , power cable  400  includes a plug  420  for connecting to an outlet  520  in external power supply device  500 , and a power line  440  connecting connector  410  and plug  420 . A charging circuit interrupt device (hereinafter, also referred to as CCID)  430  for switching between supply and interruption of the electric power from external power supply device  500  is inserted in power line  440 . 
     Power conversion device  200  is connected to inlet  220  by power lines ACL 1  and ACL 2 . Power conversion device  200  is also connected to power storage device  110  by power lines PL 2  and NL 2 , with CHR  210  interposed therebetween. 
     Power conversion device  200  is controlled in accordance with a control signal PWD provided from ECU  300 , and converts AC electric power supplied from external power supply device  500  via inlet  220  into the charging power of power storage device  110 . As described below, power conversion device  200  can also convert DC electric power provided from power storage device  110  or DC electric power generated by motor generators  130  and  135  and converted by PCU  120  into AC electric power, and supply the AC electric power to the outside of the vehicle. Power conversion device  200  may be one device capable of making bidirectional power conversion of charging and power feeding, or may include a device for charging and a device for power feeding as separate devices. 
     CHR  210  is controlled in accordance with a control signal SE 2  provided from ECU  300 , and switches between supply and interruption of electric power between power conversion device  200  and power storage device  110 . 
     PLC communication unit  230  is connected to power lines ACL 1  and ACL 2 . PLC communication unit  230  communicates with a PLC communication unit  530  included in external power supply device  500  via power cable  400  and power lines ACL 1  and ACL 2 . PLC communication unit  230  transmits vehicle information received from ECU  300  to PLC communication unit  530  in external power supply device  500 . PLC communication unit  230  also receives power supply information transmitted from PLC communication unit  530  and outputs the received power supply information to ECU  300 . 
     ECU  300  includes a CPU (Central Processing Unit), a memory device and an input/output buffer that are not shown in  FIG. 1 . ECU  300  inputs a signal provided from each sensor and the like and outputs a control signal to each device, and controls power storage device  110  and each device in vehicle  100 . It is to be noted that the control over these devices can be implemented by not only processing by software but also processing by dedicated hardware (electronic circuit). 
     Based on detected values of voltage VB and current IB provided from power storage device  110 , ECU  300  calculates a state of charge (SOC) of power storage device  110 . 
     ECU  300  receives a signal PISW indicating the connection state of power cable  400  from connector  410 . ECU  300  also receives a pilot signal CPLT from CCID  430  in power cable  400 . As described below with reference to  FIG. 2 , ECU  300  performs a charging operation based on these signals and/or information received by PLC communication unit  230 . 
     Although  FIG. 1  shows the configuration in which one control device is provided as ECU  300 , separate control devices such as a control device for PCU  120  and a control device for power storage device  110  may be provided for each function or for each device to be controlled. 
     An alarm output unit  170  receives a control signal ALM from ECU  300 , and notifies a user of information included in control signal ALM when an abnormality, a failure or the like occurs in vehicle  100 . Alarm output unit  170  includes a unit for acoustically notifying the user such as a buzzer or a chime, and a unit for visually notifying the user such as an LED, a lamp or a liquid crystal display. 
       FIG. 2  is a block diagram for describing the charging operation in  FIG. 1 . Description of elements overlapping with the elements in  FIG. 1  to which the same reference characters are allotted will not be repeated in  FIG. 2 . 
     Referring to  FIG. 2 , CCID  430  includes a CCID relay  450 , a CCID control unit  460 , a control pilot circuit  470 , an electromagnetic coil  471 , a leakage detector  480 , a voltage sensor  481 , and a current sensor  482 . Control pilot circuit  470  includes an oscillation device  472 , a resistance R 20  and a voltage sensor  473 . 
     CCID relay  450  is inserted in power line  440  in power cable  400 . CCID relay  450  is controlled by control pilot circuit  470 . When CCID relay  450  is open, an electric path in power cable  400  is interrupted. On the other hand, when CCID relay  450  is closed, electric power is supplied from external power supply device  500  to vehicle  100 . 
     Control pilot circuit  470  outputs pilot signal CPLT to ECU  300  via connector  410  and inlet  220 . This pilot signal CPLT is a signal for providing a notification of a rated current of power cable  400  from control pilot circuit  470  to ECU  300 . Pilot signal CPLT is also used as a signal for remotely controlling CCID relay  450  by ECU  300  based on the potential of pilot signal CPLT controlled by ECU  300 . Control pilot circuit  470  controls CCID relay  450  based on a change in potential of pilot signal CPLT. 
     A configuration standardized by, for example, SAE (Society of Automotive Engineers) in the United States of America, Japan Electric Vehicle Association and the like may be used as above-mentioned pilot signal CPLT and connection signal PISW, the shape of inlet  220  and connector  410 , the terminal arrangement and the like. 
     CCID control unit  460  includes a CPU, a memory device and an input/output buffer that are not shown. CCID control unit  460  inputs and outputs signals from/to each sensor and control pilot circuit  470 , and controls the charging operation of power cable  400 . 
     When the potential of pilot signal CPLT detected by voltage sensor  473  is a defined potential (e.g., 12 V), oscillation device  472  outputs a non-oscillating signal. When the potential of pilot signal CPLT becomes lower than the above-mentioned defined potential (e.g., 9 V), oscillation device  472  outputs a signal controlled by CCID control unit  460  and oscillating at a defined frequency (e.g., 1 kHz) and duty cycle. 
     The potential of pilot signal CPLT is controlled by ECU  300 . The duty cycle is set based on the rated current that can be supplied from external power supply device  500  to vehicle  100  via power cable  400 . 
     When the potential of pilot signal CPLT becomes lower than the defined potential as described above, pilot signal CPLT oscillates at a defined cycle. A pulse width of pilot signal CPLT is set based on the rated current that can be supplied from external power supply device  500  to vehicle  100  via power cable  400 . In other words, in accordance with a duty indicated by a ratio of the pulse width to this oscillation cycle, a notification of the rated current is provided from control pilot circuit  470  to ECU  300  in vehicle  100  using pilot signal CPLT. 
     It is to be noted that the rated current is defined for each power cable. The rated current varies depending on the type of power cable  400 . Therefore, the duty of pilot signal CPLT also varies depending on the type of power cable  400 . 
     Based on the duty of pilot signal CPLT received via a control pilot line L 1 , ECU  300  can sense the rated current that can be supplied to vehicle  100  via power cable  400 . 
     When the potential of pilot signal CPLT is further lowered (e.g., 6 V) by ECU  300 , control pilot circuit  470  supplies a current to electromagnetic coil  471 . Upon being supplied with the current from control pilot circuit  470 , electromagnetic coil  471  generates electromagnetic force and closes a contact point of CCID relay  450  to bring CCID relay  450  into conduction. 
     Leakage detector  480  is provided within CCID  430  and inserted in power line  440  of power cable  400 , and detects presence or absence of leakage. Specifically, leakage detector  480  detects equilibrium of currents flowing through a pair of power lines  440  in the direction opposite to each other, and senses occurrence of leakage when the equilibrium breaks. Although not specifically shown, when leakage detector  480  detects leakage, power feeding to electromagnetic coil  471  is interrupted and the contact point of CCID relay  450  is opened to bring CCID relay  450  out of conduction. 
     When plug  420  in power cable  400  is inserted into outlet  520 , voltage sensor  481  detects a power supply voltage transmitted from external power supply device  500 , and provides a notification of the detected value to CCID control unit  460 . Further, current sensor  482  detects a charging current flowing through power line  440 , and provides a notification of the detected value to CCID control unit  460 . 
     A switch SW 20  serving as a connection sensing circuit is included in connector  410 . Switch SW 20  is, for example, a limit switch and a contact point thereof is closed when connector  410  is certainly fitted into inlet  220 . When connector  410  is disconnected from inlet  220 , and when connector  410  is not fitted into inlet  220  appropriately, the contact point of switch SW 20  is opened. The contact point of switch SW 20  is also opened when an operation unit (not shown) provided at connector  410  and operated by the user at the time of removing connector  410  from inlet  220  is operated. 
     In the state in which connector  410  is disconnected from inlet  220 , a voltage signal defined by a voltage of a power supply node  350  included in ECU  300  and a pull-up resistance R 10  are generated as connection signal PISW at a connection signal line L 3 . In the state in which connector  410  is certainly connected to inlet  220 , connection signal line L 3  is connected to a vehicle earth  360  by a ground line L 2  and connection signal line L 3  attains a ground potential. It is to be noted that switch SW 20  may be replaced with a resistance having a predetermined resistance value. In this case, in the state in which connector  410  is certainly connected to inlet  220 , a potential defined by a voltage of power supply node  350 , pull-up resistance R 10 , and the resistance are generated at connection signal line L 3 . 
     By detecting a potential of connection signal line L 3  (i.e., a potential of connection signal PISW), ECU  300  can determine the connection state of connector  410 . 
     In vehicle  100 , ECU  300  further includes a CPU  310 , a resistance circuit  320 , and input buffers  330  and  340 , in addition to above-mentioned power supply node  350  and pull-up resistance R 10 . 
     Resistance circuit  320  includes pull-down resistances R 1  and R 2 , and switches SW 1  and SW 2 . Pull-down resistance R 1  and switch SW 1  are serially connected between vehicle earth  360  and control pilot line L 1  via which pilot signal CPLT is communicated. Pull-down resistance R 2  and switch SW 2  are also serially connected between vehicle earth  360  and control pilot line L 1 . In accordance with control signals S 1  and S 2  provided from CPU  310 , switches SW 1  and SW 2  are controlled to be brought into or out of conduction, respectively. 
     This resistance circuit  320  is a circuit for controlling the potential of pilot signal CPLT from the vehicle  100  side. 
     Input buffer  330  receives pilot signal CPLT of control pilot line L 1 , and outputs received pilot signal CPLT to CPU  310 . Input buffer  340  receives connection signal PISW from connection signal line L 3  connected to switch SW 20  in connector  410 , and outputs received connection signal PISW to CPU  310 . A voltage is applied to connection signal line L 3  by ECU  300  as described above, and when connector  410  is connected to inlet  220 , the potential of connection signal PISW changes. CPU  310  detects this potential of connection signal PISW, thereby detecting the connection state of connector  410 . 
     CPU  310  receives pilot signal CPLT and connection signal PISW from input buffers  330  and  340 , respectively. CPU  310  detects the potential of connection signal PISW, and detects the connection state and the fitting state of connector  410 . CPU  310  also senses the oscillation state and the duty cycle of pilot signal CPLT, thereby detecting the rated current of power cable  400 . 
     Based on the potential of connection signal PISW and the oscillation state of pilot signal CPLT, CPU  310  controls control signals S 1  and S 2  of switches SW 1  and SW 2 , thereby controlling the potential of pilot signal CPLT. As a result, CPU  310  can remotely control CCID relay  450 . Thus, electric power is transmitted from external power supply device  500  to vehicle  100  via power cable  400 . 
     In addition, CPU  310  is configured to be capable of receiving and transmitting a signal from/to PLC communication unit  230  connected to power lines ACL 1  and ACL 2 . CPU  310  transmits vehicle information to external power supply device  500  via PLC communication unit  230 , and receives power supply information transmitted from external power supply device  500  via PLC communication unit  230 . 
     Referring to  FIGS. 1 and 2 , when the contact point of CCID relay  450  is closed, AC electric power from external power supply device  500  is provided to power conversion device  200 , and preparation for charging power storage device  110  by external power supply device  500  is completed. CPU  310  outputs control signal PWD to power conversion device  200 , and thereby the AC electric power provided from external power supply device  500  is converted into the DC electric power with which power storage device  110  can be charged. Then, CPU  310  outputs control signal SE 2  to close a contact point of CHR  210 , and thereby charging of power storage device  110  is carried out. 
       FIG. 3  is an overall block diagram of another charging system  10 A including vehicle  100  according to the present embodiment. In charging system  10 A, a power cable  400 A does not include CCID  430  as in power cable  400  in  FIG. 1 . Instead, an external power supply device  500 A includes a CCID  540 .  FIG. 4  is a block diagram for describing a charging operation in  FIG. 3 . 
     Description of elements overlapping with the elements in  FIGS. 1 and 2  will not be repeated in  FIGS. 3 and 4 . In addition, the configuration of CCID  540  in  FIG. 4  is basically the same as the configuration of CCID  430  in  FIG. 2 , and thus, detailed description thereof will not be repeated. 
     Referring to  FIGS. 3 and 4 , CCID  540  is inserted in a power line connecting AC power source  510  and an outlet  520 A in external power supply device  500 A. In addition, control pilot line L 1  and ground line L 2  in vehicle  100  are connected to CCID  540  via power cable  400 A. 
     PLC communication unit  530  is connected to a power line connecting CCID  540  and outlet  520 A. In charging system  10 A, CCID  540  is included in external power supply device  500 A. Therefore, the current capacity of connected power cable  400 A is set in accordance with input by the user, or when power cable  400 A is fixedly connected to external power supply device  500 A, the duty of pilot signal CPLT is set to a fixed value. 
     [Problems of Charging System] 
     In charging systems  10  and  10 A, the charging operation can be started/stopped and the signals related to the rated current of the power cable can be received/transmitted based on the potential and the duty of pilot signal CPLT. In these systems like smart grid, however, various information is further required such as the state of charge of the vehicle, the estimated time of next running, the state of other devices connected to the external power supply device, or a power feeding request command to the vehicle. Therefore, in charging systems  10  and  10 A, these information is transmitted by the PLC communication using PLC communication units  230  and  530 , in addition to the information transmitted using pilot signal CPLT. 
     In the case of a system like charging system  1  OA shown in  FIGS. 3 and 4 , even when a CCID relay  550  included in CCID  540  is open, communication can be established because PLC communication unit  230  and PLC communication unit  530  are connected by power cable  400 A. 
     In charging system  10  shown in  FIGS. 1 and 2 , however, when CCID relay  450  in power cable  400  is opened, PLC communication unit  230  is disconnected from PLC communication unit  530 , and thus, the PLC communication cannot be established. In this case, prior to establishing the PLC communication, CCID relay  450  must be closed. 
     Furthermore, in the case of a system in which the external power supply device does not have the PLC communication unit, or when the PLC communication unit in the external power supply device cannot establish communication due to a failure and the like, the PLC communication cannot be established even if vehicle  100  has PLC communication unit  230 . In such a case, the charging operation must be performed based on the state of pilot signal. CPLT. 
     As described above, in the charging system, a method for communication with the power cable and the external power supply device varies depending on the configuration of the power cable and the external power supply device connected to the vehicle, Therefore, if the communication method is not selected in accordance with the system configuration, the appropriate charging operation may be impossible. 
     Therefore, in the present embodiment, in the vehicle having the PLC communication function and capable of external charging, there is performed charging control by which the charging operation is performed using the appropriate communication method in accordance with the configuration of the power cable and the external power supply device in the charging system. 
     [Description of Charging Control in the Present Embodiment] 
     The charging operation in different system configurations will be described with reference to time charts in  FIGS. 5 to 7 .  FIG. 5  is a time chart when the PLC communication is possible regardless of the operating state of the CCID relay, as in charging system  10 A shown in  FIGS. 3 and 4 .  FIG. 6  is a time chart when the PLC communication is possible with the CCID relay closed, as in charging system  10  shown in  FIGS. 1 and 2 .  FIG. 7  is a time chart when the external power supply device does not include the PLC communication unit or when the PLC communication is impossible due to a failure and the like occurring in the PLC communication unit. 
     First, referring to  FIGS. 4 and 5 , before time t 1 , connector  410  is not connected to inlet  220 . In this state, pilot signal CPLT is at a potential V 1  (e.g., 12 V) and in the non-oscillating state, and the potential of connection signal PISW is at a potential V 11  defined by power supply node  350 . 
     At time t 1 , connector  410  is connected to inlet  220 . Then, switch SW 20  included in connector  410  is closed, and thereby connection signal line L 3  is connected to ground line L 2  and the potential of connection signal PISW attains the ground potential. As a result, CPU  310  recognizes that connector  410  has been connected to inlet  220 . In response to this, CPU  310  renders control signal S 1  active and brings switch SW 1  into conduction (time t 2 ). As a result, the potential of pilot signal CPLT decreases to V 2  (e.g., 9 V), and in response to this, an oscillation device  572  in CCID  540  starts oscillation of pilot signal CPLT (time t 4 ). 
     In addition, when connector  410  is connected to inlet  220 , CPU  310  starts transmission of a signal from PLC communication unit  230  to PLC communication unit  530  in external power supply device  500 A (time t 3 ). Since the PLC communication is possible regardless of the operating state of CCID relay  550  in charging system  10 A, PLC communication unit  530  in external power supply device  500 A transmits a response signal to the signal provided from PLC communication unit  230  on the vehicle  100  side. Upon receiving the response signal from PLC communication unit  530  in external power supply device  500 A, CPU  310  recognizes that the PLC communication has been established (time t 5 ). 
     When the PLC communication between vehicle  100  and external power supply device  500 A is established, CPU  310  obtains the power supply information (such as, for example, a supplied voltage, a supplied current, the current capacity of the power cable) for charging by external power supply device  500 A, and makes preparation for charging based on the information. In this case, CPU  310  gives a higher priority to the information obtained by the PLC communication than to the duty of pilot signal CPLT. 
     Then, at time t 6 , CPU  310  renders control signal S 2  active and brings switch SW 2  into conduction. Then, the potential of pilot signal CPLT decreases to V 3  (e.g., 6 V). In response to this, CCID relay  550  in CCID  540  is closed (time t 7 ), and electric power is supplied from external power supply device  500 A to vehicle  100 . 
     At time t 8 , CPU  310  drives CHR  210  ( FIG. 3 ) and power conversion device  200  ( FIG. 3 ), thereby starting a charging process. 
     Thereafter, charging of power storage device  110  ( FIG. 3 ) proceeds, and at time t 9 , the charging process ends. In response to this, the PLC communication is stopped (time t 10 ). Furthermore, control signal S 2  is rendered inactive, switch SW 2  is brought out of conduction, and the potential of pilot signal CPLT rises to V 2 . In response to this, at time t 11 , CCID relay  550  is opened and the electric power supply from external power supply device  500 A to vehicle  100  is stopped. 
     When the user finally pulls connector  410  out of inlet  220  (time t 12 ), the potential of connection signal PISW recovers to V 11 . In response to this, control signal S 1  is rendered inactive and switch SW 1  is brought out of conduction. Then, the potential of pilot signal CPLT recovers to V 1 . 
     Next, the case of charging system  10  shown in  FIGS. 1 and 2  will be described with reference to  FIG. 6 . 
     Referring to  FIGS. 2 and 6 , before time t 24 , a process similar to the process before time t 4  in  FIG. 5  is executed. When CPU  310  recognizes that connector  410  has been connected to inlet  220 , CPU  310  starts transmission of the signal from PLC communication unit  230  to PLC communication unit  530  in external power supply device  500 . 
     In charging system  10 , however, CCID  430  is provided in power cable  400 . Therefore, PLC communication unit  530  in external power supply device  500  cannot receive the signal provided from PLC communication unit  230  on the vehicle  100  side, and does not output the response signal thereto. 
     When CPU  310  recognizes that the response signal from PLC communication unit  530  in external power supply device  500  is not received during a predetermined time period after transmission of the signal from PLC communication unit  230  started (time t 25 ), CPU  310  suspends transmission of the signal from PLC communication unit  230 , renders control signal S 2  active and brings switch SW 2  into conduction (time t 26 ). 
     As a result, the potential of pilot signal CPLT decreases to V 2 . In response to this, CCID relay  450  is closed (time t 27 ). As a result, electric power from external power supply device  500  is supplied to vehicle  100 , and PLC communication units  230  and  530  are connected. 
     In this state, CPU  310  retransmits the signal to external power supply device  500  via PLC communication unit  230  (time t 28 ). In this case, CCID relay  450  is closed, and thus, PLC communication unit  530  in external power supply device  500  can receive the signal provided from PLC communication unit  230 , and outputs the response signal thereto. 
     Upon receiving the response signal from PLC communication unit  530  in external power supply device  500  (time t 29 ), CPU  310  starts the PLC communication with external power supply device  500 , and executes the charging process based on the power supply information provided from external power supply device  500  (time t 30 ). The subsequent charging end process is similar to that described with reference to time t 9  and the subsequent times in  FIG. 5 . 
     As described above,  FIG. 7  is a time chart when the external power supply device does not have the PLC communication unit or when the PLC communication unit cannot establish communication due to a failure and the like. In this case, CPU  310  does not receive the response signal to the transmission signal provided from PLC communication unit  230  in vehicle  100 . 
     Referring to  FIG. 7 , before time t 48 , a process similar to the process before time t 28  in  FIG. 6  is executed. CPU  310  first transmits the signal from PLC communication unit  230  in vehicle  100  to the external power supply device, with the CCID relay being open. In response to the fact that the response signal is not received, CPU  310  suspends transmission of the signal from PLC communication unit  230  (time t 45 ). Thereafter, CPU  310  closes the CCID relay (time t 47 ), and retransmits the signal from PLC communication unit  230  to the external power supply device (time t 48 ). 
     In the case shown in  FIG. 7 , the response signal from the PLC communication unit on the external power supply device side is not received in retransmission of the signal as well. Therefore, at time t 49 , CPU  310  stops transmission of the signal from PLC communication unit  230  to the external power supply device, and reads the duty of pilot signal CPLT and recognizes the rated current of the power cable. 
     Thereafter, CPU  310  sets the charging current based on the rated current of the power cable, and starts the charging operation at time t 50 . The subsequent charging end process is similar to that described with reference to time t 9  and the subsequent times in  FIG. 5 . 
     As described above, in the present embodiment, the vehicle can appropriately obtain the information required for the charging operation using the PLC communication or the pilot signal, in accordance with the configuration of the power cable and the external power supply device connected to the vehicle during external charging. 
       FIG. 8  is a flowchart for describing the charging process executed by ECU  300  in the present embodiment. The flowchart shown in  FIG. 8  is implemented by calling a program prestored in ECU  300  from the main routine and executing the program at a predetermined cycle. Alternatively, a part of the steps can also be implemented by dedicated hardware (electronic circuit). 
     Referring to  FIG. 8 , in step (hereinafter, the step will be abbreviated as “S”)  100 , ECU  300  determines whether or not connector  410  in the power cable is connected, based on the potential of connection signal PISW. 
     If connector  410  is not connected (NO in S 100 ), external charging is not carried out, and thus, ECU  300  ends the process. 
     If connector  410  is connected (YES in S 100 ), the process proceeds to S 110 . ECU  300  renders control signal S 1  active and brings switch SW 1  into conduction. As a result, a potential Vcplt of pilot signal CPLT changes from V 1  to V 2 . 
     In response to the fact that potential Vcplt of pilot signal CPLT decreases to V 2 , and more specifically the fact that potential Vcplt of pilot signal CPLT falls within a first range (V 3 &lt;Vcplt≦V 2 ), the CCID causes pilot signal CPLT to oscillate. 
     Then, in S 120 , ECU  300  starts transmission of the signal via PLC communication unit  230  to PLC communication unit  530  in the external power supply device, and determines whether or not the response signal from PLC communication unit  530  to the transmission signal is present (S 130 ). 
     If the response signal from PLC communication unit  530  is present (YES in S 130 ), the process proceeds to S 145 . ECU  300  continues the PLC communication with PLC communication unit  530  in the external power supply device and obtains the power supply information provided from the external power supply device. 
     Thereafter, in S 155 , ECU  300  renders control signal S 2  active and brings switch SW 2  into conduction. As a result, potential Vcplt of pilot signal CPLT changes from V 2  to V 3 . Then, in response to the fact that potential Vcplt of pilot signal CPLT decreases to V 3 , and more specifically the fact that potential Vcplt of pilot signal CPLT falls within a second range (Vcplt≦V 3 ), the CCID closes the CCID relay. As a result, electric power is supplied from the external power supply device to vehicle  100 . 
     Then, in S 200 , ECU  300  executes the charging process based on the power supply information obtained in S 145 . 
     On the other hand, if the response signal from PLC communication unit  530  is not present in S 130  (NO in S 130 ), the process proceeds to S 140 . ECU  300  suspends transmission of the signal to PLC communication unit  530  in the external power supply device. 
     Then, ECU  300  renders control signal S 2  active and brings switch SW 2  into conduction As a result, potential Vcplt of pilot signal CPLT changes from V 2  to V 3 , and the CCID relay is closed as described above (S 150 ). As a result, electric power is supplied from the external power supply device to vehicle  100 . 
     Thereafter, in S 160 , ECU  300  restarts transmission of the signal to PLC communication unit  530  in the external power supply device, and again determines whether or not the response signal from PLC communication unit  530  to the transmission signal is present (S 160 ). 
     If the response signal from PLC communication unit  530  is present (YES in S 160 ), the process proceeds to S 185 . ECU  300  continues the PLC communication with PLC communication unit  530  in the external power supply device and obtains the power supply information provided from the external power supply device. Thereafter, the process proceeds to S 200  and ECU  300  executes the charging process based on the obtained power supply information. 
     If the response signal from PLC communication unit  530  is not present (NO in S 160 ), the process proceeds to S 180 . ECU  300  determines that the external power supply device does not have the PLC communication unit or that the PLC communication unit cannot establish communication due to a failure and the like, and stops transmission of the signal to PLC communication unit  530 . At this time, ECU  300  also outputs an alarm to alarm output unit  170  and notifies the user that the PLC communication cannot be established between vehicle  100  and the external power supply device. 
     In S 190 , ECU  300  reads the duty Duty of pilot signal CPLT, thereby determining the rated current of the power cable. Then, in S 200 , ECU  300  executes the charging process based on the rated current. 
     With the control in accordance with the above-mentioned process, in the charging system including the vehicle having the PLC communication function, the communication method can be selected in accordance with the configuration of the power cable and the external power supply device, and the power supply information for external charging can be appropriately obtained. As a result, in both of the case where the PLC communication is possible without closing the CCID relay and the case where the PLC communication is possible by closing the CCID relay, the power supply information can be appropriately obtained by the PLC communication. In addition, when the PLC communication is impossible, the charging process can be executed based on pilot signal CPLT. Therefore, even in the case of a different configuration of the power cable and the external power supply device, the charging process can be appropriately executed. 
     Although the case of external charging from the external power supply device to the vehicle has been described above, the present invention is also applicable to the case of supplying electric power stored in the vehicle or electric power generated at the vehicle to a device or power network external to the vehicle. In this case, the step in S 200  in the flowchart shown in  FIG. 8  is changed into a discharging process, and thereby the ECU may transmit the vehicle information such as the state of charge of the vehicle and specifications of the power conversion device to a control device in the device or power network external to the vehicle by the PLC communication, and may receive an electric power supply command from the device or power network external to the vehicle and supply electric power from the vehicle based on the received command. In addition, when the PLC communication is impossible, the ECU may recognize that now is in an electric power supply mode as well as an output current to be supplied, based on the duty (or potential, frequency and the like) of the pilot signal, and may supply electric power from the vehicle based on the recognition. 
     “CCID  430 ,  540 ” in the present embodiment is one example of “switching device” in the present invention. In addition, “control pilot circuit  470 ,  570 ” in the present embodiment is one example of “signal generation unit” in the present invention. 
     It should be understood that the embodiments disclosed herein are illustrative and not limitative in any respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. 
     REFERENCE SIGNS LIST 
     
         
         
           
               10 ,  10 A charging system;  100  vehicle;  110  power storage device;  115  SMR;  120  PCU;  121  converter;  122 ,  123  inverter;  130 ,  135  motor generator;  140  motive power transmission gear;  150  driving wheel;  160  engine;  170  alarm output unit;  200  power conversion device;  210  CHR;  220  inlet;  230 ,  530  PLC communication unit;  300  ECU;  310  CPU;  320  resistance circuit;  330 ,  340  input buffer;  350  power supply node;  360  vehicle earth;  400 ,  400 A power cable;  410  connector;  420  plug;  430 ,  540  CCID;  440  power line;  450 ,  550  CCID relay;  460 ,  560  CCID control unit;  470 ,  570  control pilot circuit;  471 ,  571  electromagnetic coil;  472 ,  572  oscillation device;  473 ,  573  voltage sensor;  480 ,  580  leakage detector;  481 ,  581  voltage sensor;  482 ,  582  current sensor;  500 ,  500 A external power supply device;  510  AC power source;  520 ,  520 A outlet; ACL 1 , ACL 2 , PL 1 , PL 2 , NL 1 , NL 2  power line; C 1 , C 2  capacitor; L 1  control pilot line; L 2  ground line; L 3  connection signal line; R 1 , R 2 , R 10 , R 20 , R 50  resistance; SW 1 , SW 2 , SW 20  switch