Abstract:
A power management device of a power system manages the power generation quantity of the whole power system. A power generation control device controls a power generation device using a power generation command value (Ifccon1req) of the power generation device, said power generation command value having been acquired from the power management device via a first signal system, and a parameter (Ibat) that is directly acquired from a parameter acquisition unit via a second signal system.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an electric power system. 
       BACKGROUND ART 
       [0002]    A hybrid electronic control unit (70) of U.S. Patent Application Publication No. 2008/0018111 (hereinafter referred to as the “US 2008/0018111 A1”), sets a drive point of an engine (22) and torque commands Tm1* and Tm2* of motors MG1 and MG2 in a range between an input limit and an output limit of a battery (50), in order to satisfy a preset output power demand. Further, the hybrid electronic control unit (70) sends the drive point of the engine (22) to an engine ECU (24) and the torque commands Tm1* and Tm2* to a motor ECU (40), together with the input limit and the output limit of the battery (50) to the motor ECU (40) (Abstract). 
         [0003]    The motor ECU (40) verifies whether the operations of the motors MG1 and MG2 with the torque commands Tm1* and Tm2* are in the range between the input limit and the output limit of the battery (50). When the operations of the motors MG1 and MG2 are out of the range between the input limit and the output limit of the battery (50), the motor ECU (40) resets the torque commands Tm2* and Tm2* to make the operations of the motors MG1 and MG2 in the range between the input limit and the output limit and controls the operations of the motors MG1 and MG2 with the reset torque commands Tm1* and Tm2*. This arrangement effectively prevents the battery from being overcharged with excessive electric power or from being over-discharged to supply excessive electric power even in the state of electric power imbalance due to a communication lag (Abstract). 
         [0004]    The communication lag herein means a time delay by communication (paragraph [0003]). More specifically, the communication lag occurs in a period from the timing of making operation commands (torque command Tm1*, torque command Tm2*) to the timing of controlling the operations of power generation means (engine 22) or electric motors (motors MG1, MG2) ([0007]). 
       SUMMARY OF INVENTION 
       [0005]    As described above, US 2008/0018111 A1 describes a technique aimed to protect the battery by limiting the output of the power generation means (engine 22) and the electric motors (motor MG1, MG2). However, from the viewpoint of protecting the battery (energy storage device), there is room for making further improvements. 
         [0006]    For example, in US 2008/0018111 A1, the motor control routine (FIG. 8) is repeatedly performed by the motor ECU (40) at preset time intervals, for example, at every several msec. (last line of paragraph [0057]). The routine includes a series of flows from the acquisition (S200) of the torque commands Tm1*, Tm2*, motor rotation speeds Nm1, Nm2, and battery input and output limits Win, Wout, to the control (S300) of the battery motors MG1, MG2 by the torque commands Tm1*, Tm2* (FIG. 8). Therefore, it appears that the acquisition cycle of the torque commands Tm1*, Tm2*, and the control cycle of the motors MG1, MG2 are the same. 
         [0007]    In this regard, in the case where there are constraints with the communication cycles (i.e., acquisition cycle of the torque commands Tm1*, Tm2*, etc.) between the hybrid electronic control unit (70) and the motor ECU (40), rapid changes in the input to, or the output from the battery may not be handled. Such rapid changes may include, for example, rapid increase in the input electric power (electrical energy) to the battery due to the sharp decrease in power consumption of the drive motor due to locking of the wheels, etc. 
         [0008]    The present invention has been made taking the above problems into account, and an object of the present invention is to provide an electric power system in which it is possible to protect an energy storage device more appropriately. 
         [0009]    According to an aspect of the present invention, an electric power system includes a power generation device, an energy storage device, a drive motor driven by electric power from the power generation device and the energy storage device, a power generation control unit configured to control a power generation amount of the power generation device, a parameter acquisition unit configured to obtain a parameter regarding an input to, or an output from the energy storage device, an electric power management unit provided separately from the power generation control unit, a first signal system connecting the power generation control unit and the electric power management unit, and a second signal system bypassing the electric power management unit and connecting the power generation control unit and the parameter acquisition unit. The power management unit is configured to manage an amount of power generation of the electric power system as a whole, and the power generation control unit is configured to use a power generation command value of the power generation device obtained from the electric power management unit through the first signal system and the parameter obtained from the parameter acquisition unit through the second signal system to control the power generation device. 
         [0010]    In the present invention, the power generation control unit uses the power generation command value of the power generation device obtained from the power generation management unit through the first signal system and the parameter obtained from the parameter acquisition unit through the second signal system to control the power generation device. Therefore, for example, in the normal state, the power generation command value is used mainly, and if an instantaneous change occurs in parameters regarding inputs to, or outputs from the energy storage device (e.g., rapid increase in the input electric power to the energy storage device resulting from rapid decrease in the power consumption of the drive motor due to locking of the wheels, etc.), by focusing on the change of parameter, it becomes possible to control power generation of the energy storage device. Therefore, it becomes possible to protect the energy storage device responsive to the rapid change in the input to, or output from the energy storage device. 
         [0011]    The power generation control unit may be configured to correct a power generation command value of the power generation device obtained from the electric power management unit through the first signal system or a limit value of the power generation command value using the parameter obtained from the parameter acquisition unit through the second signal system, to control the power generation device. In this manner, it becomes possible to protect the energy storage device by avoiding the rapid change in the input to or the output from the energy storage device. 
         [0012]    The electric power generation control unit may be configured to obtain the power generation command value of the power generation device from the electric power management unit through the first signal system at a first cycle. The parameter may be obtained from the parameter acquisition unit through the second signal system at a second cycle which is shorter than the first cycle, and control of the power generation device using the power generation command value corrected using the parameter may be implemented at a third cycle which is smaller than the first cycle. 
         [0013]    In the present invention, the power generation control unit corrects the power generation command value of the power generation device obtained from the electric power management unit through the first signal system or the limit value of the power generation command value using the parameter obtained from the parameter acquisition unit through the second signal system to control the power generation device. Further, the cycle (second cycle) of obtaining the parameter and the cycle (third cycle) of controlling the power generation device are shorter than the cycle (first cycle) of obtaining the power generation command value of the power generation device. Therefore, it becomes possible to control power generation of the power generation device responsive to the instantaneous change in the parameter (e.g., rapid increase in the input electric power to the energy storage device resulting from rapid decrease in the power consumption of the drive motor due to locking of the wheels, etc.). Accordingly, by avoiding the rapid charge in the input to or the output from the energy storage device, it becomes possible to protect the energy storage device. 
         [0014]    The power generation control unit may be configured to limit an output from the power generation device when input electric power to the energy storage device exceeds an input electric power threshold value, or to increase the output from the power generation device when output electric power from the energy storage device exceeds an output electric power threshold value. 
         [0015]    According to the above system, when the input electric power to the energy storage device exceeds the input electric power threshold value, the output of the power generation device is limited. In this manner, the input electric power to the energy storage device is decreased, and overcharging of the energy storage device is avoided. Thus, it becomes possible to protect the energy storage device. Otherwise, when the output electric power from the energy storage device exceeds the output electric power threshold value, the output of the power generation device is increased. In this manner, the output electric power from the energy storage device is decreased, and overdischarging of the energy storage device is avoided. Thus, it becomes possible to protect the energy storage device. 
         [0016]    The power generation device may include a fuel cell, and the power generation control unit may include a first converter provided for the fuel cell, and a first converter control unit configured to control the first converter. The electric power system may include a second converter provided for the energy storage device and a second converter control unit configured to control the second converter. When the input electric power to the energy storage device exceeds the input electric power threshold value, the first converter control unit may be configured to limit an output current of the fuel cell, and change an output current limit value of the fuel cell based on the input electric power threshold value of the energy storage device, or when the output electric power from the energy storage device exceeds the output electric power threshold value, the first converter control unit may be configured to increase the output current of the fuel cell, and change an output current limit value of the fuel cell based on the output electric power threshold value of the energy storage device. 
         [0017]    In this manner, it becomes possible to impose a suitable limitation to the output current of the fuel cell in correspondence with the input electric power threshold value or the output electric power threshold value of the energy storage device. 
         [0018]    The input electric power threshold value or the output electric power threshold value of the energy storage device may be determined based on a remaining capacity of the energy storage device or a temperature of the energy storage device. In this manner, it becomes possible to suitably set the input electric power threshold value or the output electric power threshold value of the energy storage device, and thus, impose a suitable limitation to the output current of the fuel cell as well. 
         [0019]    The first converter control unit may be configured to correct outputs of the fuel cell based on a deviation between the input electric power and the input electric power threshold value of the energy storage device or a deviation between the output electric power and the output electric power threshold value of the energy storage device. In this manner, based on the deviation between the input electric power of the energy storage device and the input electric power threshold value of the energy storage device, or the deviation between the output electric power of the energy storage device and the output electric power threshold value of the energy storage device, it becomes possible to suitably correct the output of the fuel cell. 
         [0020]    A load which is different from the drive motor may be connected to a power line connecting the energy storage device and the second converter, and the first converter control unit may be configured to estimate input electric power to the energy storage device or output electric power from the energy storage device based on primary electric power of the second converter. In this manner, it becomes possible to monitor the state of the energy storage device. Accordingly, it becomes possible to determine the design more freely, and excellent failsafe characteristics are achieved. 
         [0021]    The first converter control unit may be configured to estimate the input electric power to the energy storage device or the output electric power from the energy storage device based on secondary electric power of the second converter. In this manner, it becomes possible to monitor the state of the energy storage device. Accordingly, it becomes possible to determine the design more freely, and excellent failsafe characteristics are achieved. 
         [0022]    According to another aspect of the present invention, an electric power system according to the present invention includes a power generation device, an energy storage device, a drive motor driven by electric power from the power generation device and the energy storage device, a motor control unit configured to control an output from the drive motor, a power generation control unit configured to control a power generation amount of the power generation device, a parameter acquisition unit configured to obtain a parameter regarding an input to, or an output from the energy storage device, an electric power management unit provided separately from the motor control unit and the power generation control unit, a first signal system connecting the motor control unit and the electric power management unit, and a second signal system bypassing the electric power management unit and connecting the motor control unit and the parameter acquisition unit. In the electric power system, the motor control unit is configured to use an output command value of the drive motor obtained from the electric power management unit through the first signal system and the parameter obtained from the parameter acquisition unit through the second signal system to control the drive motor. 
         [0023]    In the present invention, the motor control unit uses an output command value of the drive motor obtained from the electric power management unit through the first signal system and the parameter obtained from the parameter acquisition unit through the second signal system to control the drive motor. Therefore, for example, in the normal state, the output command value is used mainly, and if an instantaneous change occurs in parameters regarding inputs to, or outputs from the energy storage device (e.g., rapid increase in the output electric power from the energy storage device resulting from rapid increase in the power consumption of the drive motor due to skidding of the wheels, etc.), by focusing on the change of the parameters, etc., it becomes possible to control power generation of the power generation device. Therefore, it becomes possible to protect the energy storage device responsive to the rapid change in the input to, or output from the energy storage device. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0024]      FIG. 1  is diagram schematically showing overall structure a fuel cell vehicle as an electric power system according to a first embodiment of the present invention; 
           [0025]      FIG. 2  is a flow chart for controlling an FC converter by an FC converter electronic control unit in the first embodiment; 
           [0026]      FIG. 3  is a diagram illustrating calculation of target primary current of the FC converter in the first embodiment; 
           [0027]      FIG. 4  is a flow chart (details of S 3  in  FIG. 2 ) for calculating the target primary current of the FC converter, in the first embodiment; 
           [0028]      FIG. 5  is a flow chart (details of S 11  in  FIG. 4 ) for calculating a primary current limit value of the FC converter from a viewpoint of protecting a battery, in the first embodiment; 
           [0029]      FIG. 6  is a flow chart (details of S 14  of  FIG. 4 ) for calculating a feedback correction value of primary current of the FC converter, in the first embodiment; 
           [0030]      FIG. 7  is a diagram schematically showing overall structure of a fuel cell vehicle as an electric power system according to a second embodiment of the present invention; 
           [0031]      FIG. 8  is a diagram illustrating calculation of target primary current of the FC converter in the second embodiment; 
           [0032]      FIG. 9  is a flow chart (details of S 14  of  FIG. 4 ) for calculating a feedback correction value of primary current of the FC converter, in the second embodiment; 
           [0033]      FIG. 10  is a time chart showing various sensor values and control values in a vehicle according to a comparative example; 
           [0034]      FIG. 11  is a time chart showing various sensor values and control values in a fuel cell vehicle according to the second embodiment; 
           [0035]      FIG. 12  is diagram schematically showing overall structure of a fuel cell vehicle as an electric power system according to a third embodiment of the present invention; 
           [0036]      FIG. 13  is a diagram illustrating calculation of target primary current of the FC converter in the third embodiment; 
           [0037]      FIG. 14  is a flow chart (details of S 14  of  FIG. 4 ) for calculating a feedback correction value of primary current of the FC converter, in the third embodiment; 
           [0038]      FIG. 15  is a diagram schematically showing overall structure of a fuel cell vehicle as an electric power system according to a fourth embodiment of the present invention; 
           [0039]      FIG. 16  is a flow chart for battery protection control by a motor electronic control unit in the fourth embodiment; and 
           [0040]      FIG. 17  is a block diagram schematically showing structure of a modified example of the fuel cell vehicle according to the first to fourth embodiments. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
     A. First Embodiment 
     [A1. Structure of First Embodiment] 
     (A1-1. Overall Structure) 
       [0041]      FIG. 1  is a diagram schematically showing overall structure of a fuel cell vehicle  10  (hereinafter referred to as the “FC vehicle  10 ” or the “vehicle  10 ” as an electric power system according to a first embodiment of the present invention. The vehicle  10  has a drive system  1000  including a traction motor  12  (hereinafter referred to as the “motor  12 ” or the “drive motor  12 ”), an inverter  14 , and a motor electronic control unit  16  (hereafter also referred to as the “motor ECU  16 ” or the “MOT ECU  16 ”). 
         [0042]    Further, the vehicle  10  has a FC system  2000  including a fuel cell stack  20  (hereinafter referred to as the “FC stack  20 ” or the “FC  20 ”), a fuel cell electronic control unit  22  (hereinafter referred to as the “FC ECU  22 ”), a fuel cell converter  24  (hereinafter referred to as the “FC converter  24 ”), an FC converter electronic control unit  26  (hereinafter referred to as the “FC converter ECU  26 ” or the “ECU  26 ”), and an air pump  28 . 
         [0043]    Further, the vehicle  10  has a battery system  3000  including a battery  30 , a battery electronic control unit  32  (hereinafter referred to as the battery ECU  32 ″ or the “BAT ECU  32 ”), a battery converter  34  (hereinafter referred to as the “BAT converter  34 ”), a battery converter electronic control unit  36  (hereinafter referred to as the “battery converter ECU  36 ” or “BAT converter ECU  36 ”). 
         [0044]    Further, the vehicle  10  includes an air conditioner  40 , a step-down (voltage buck) converter  42 , a 12V system  44 , and a management electronic control unit  50  (hereinafter also referred to as the “management ECU  50 ” or the “MG ECU  50 ”). The air pump  28 , the air conditioner  40 , the step-down converter  42 , and the 12V system  44  are auxiliary devices of the vehicle  10 , and serve as parts of the load in the vehicle  10  as the electric power system. 
       (A1-2. Drive System  1000 ) 
     (A1-2-1. Traction Motor  12 ) 
       [0045]    The motor  12  of the first embodiment is a three phase alternating current brushless motor. The motor  12  generates a driving force based on electric power supplied from the FC  20  and the battery  30 , and rotates wheels (not shown) through a transmission (not shown) using this driving force. Further, the motor  12  outputs electric power produced by regeneration (regenerative electric power Preg) [W] to the battery  30 , etc. 
       (A1-2-2. Inverter  14 ) 
       [0046]    The inverter  14  has three-phase full bridge structure, and performs DC to AC conversion. More specifically, the inverter  14  converts the direct current into three-phase alternating current, and supplies the alternating current to the motor  12 , and after AC to DC conversion as a result of regenerative operation, supplies the direct current to the battery  30 , etc. through the battery converter  34 . The motor  12  and the inverter  14  are main devices in the vehicle  10 , and parts of the load in the vehicle  10  as an electric power system. 
         [0047]    The input terminal voltage Vinv of the inverter  14  (hereinafter referred to as the “inverter voltage Vinv”) is detected by a voltage sensor  60 , and outputted to the motor ECU  16  through a signal line  62 . The input terminal current 
         [0048]    Iinv of the inverter  14  (hereinafter referred to as the “inverter current Iinv”) is detected by a current sensor  64 , and outputted to the motor ECU  16  through a signal line  66 . 
       (A1-2-3. Motor ECU  16 ) 
       [0049]    The motor ECU  16  controls the motor  12  and the inverter  14  based on input values such as command values from the management ECU  50 . Further, the motor ECU  16  outputs the inverter voltage Vinv, the inverter current Iinv, the inverter electric power Pinv, etc., to a communications network  70 . The inverter electric power Pinv is input terminal electric power of the inverter  14  calculated by multiplying the inverter voltage Vinv by the inverter current Iinv. In the first embodiment, the communications network  70  is a CAN (controller area network). Hereinafter, the communications network  70  is also referred to as the CAN  70 . 
         [0050]    The motor ECU  16  includes input/output devices, computing devices, and storage devices (these devices are not shown). The other ECUs also include input/output devices, computing devices, and storage devices. 
       (A1-3. FC System  2000 ) 
     (A1-3-1. FC Stack  20 ) 
       [0051]    For example, the FC stack  20  is formed by stacking a plurality of fuel cells each including an anode, a cathode, and a solid polymer electrolyte membrane interposed between the anode and the cathode. An anode system, a cathode system, a cooling system, etc. are provided around the FC stack  20 . The anode system supplies a hydrogen (fuel gas) to the anode of the FC stack  20 , and discharges the hydrogen from the anode of the FC stack  20 . The cathode system supplies air containing oxygen (oxygen-containing gas) to the cathode of the FC stack  20 , and discharges the air from the cathode of the FC stack  20 . The cooling system cools the FC stack  20 . In  FIG. 1 , the anode system, the cathode system, and the cooling system are not shown except the air pump  28  and the FC ECU  22 . 
       (A1-3-2. FC ECU  22 ) 
       [0052]    The FC ECU  22  controls the overall power generation by the FC  20  such as supply of the hydrogen and oxygen to the FC  20 , based on input values such as command values from the management ECU  50 . That is, the FC ECU  22  controls the anode system, the cathode system, and the cooling system. The FC ECU  22  transmits power consumption Pap [W] of the air pump  28  to the management ECU  50 , the FC converter ECU  26 , etc. through the CAN  70 . 
       (A1-3-3. FC Converter  24 ) 
       [0053]    The FC converter  24  is a chopper type step-up (voltage boost) voltage converter (DC/DC converter) for stepping up the output voltage of the FC  20  (hereinafter referred to as the “FC voltage Vfc”, and supplying the stepped up voltage to the inverter  14 . The FC converter  24  is provided between the FC  20  and the inverter  14 . Stated otherwise, one terminal of the FC converter  24  is connected to the primary side where the FC  20  is present, and the other terminal of the FC converter  24  is connected to the secondary side as a node between the inverter  14  and the battery  30 . 
         [0054]    The primary voltage Vfccon1 of the FC converter  24  is detected by a voltage sensor  80 , and outputted to the FC converter ECU  26  through a signal line  82 . The primary current Ifccon 1  of the FC converter  24  is detected by a current sensor  84 , and outputted to the FC converter ECU  26  through a signal line  86 . The secondary voltage Vfccon 2  of the FC converter  24  is detected by a voltage sensor  88 , and outputted to the FC converter ECU  26  through a signal line  90 . The secondary current Ifccon 2  of the FC converter  24  is detected by a current sensor  92 , and outputted to the FC converter ECU  26  through a signal line  94 . 
       (A1-3-4. FC Converter ECU  26 ) 
       [0055]    The FC converter ECU  26  controls the FC  20  through the FC converter  24  based on input values such as command values from the management ECU  50 . Hereinafter, the FC converter  24  and the FC converter ECU  26  will be referred to as the “FC VCU  96 ” as having a meaning of a voltage control unit for the FC  20 . 
         [0056]    Some of the input values to the FC converter ECU  26  are directly inputted to the FC converter ECU  26 , and the other input values are inputted to the FC converter ECU  26  through the communications network  70 . In the first embodiment, the input values directly inputted to the FC converter ECU  26  include input/output terminal current Ibat of the battery  30  detected by a current sensor  104  described later. Therefore, it becomes possible to protect the battery  30  (The detailed explanation will be given later.). 
       (A1-4. Battery System  3000 ) 
     (A1-4-1. Battery  30 ) 
       [0057]    The battery  30  is an energy storage device including a plurality of battery cells. For example, a lithium ion secondary battery, a nickel-metal hydride (nickel hydrogen) secondary battery, etc. may be used. In the first embodiment, the lithium ion secondary battery is used. Instead of the battery  30 , an energy storage device such as a capacitor may be used. 
         [0058]    The input/output terminal voltage [V] of the battery  30  (hereinafter referred to as the “BAT terminal voltage Vbat” is detected by a voltage sensor  100 , and outputted to the battery ECU  32  through a signal line  102 . The input/output terminal current [A] of the battery  30  (hereinafter referred to as the “BAT terminal current Ibat” is detected by the current sensor  104 , and outputted to the FC converter ECU  26  and the battery ECU  32  through a signal line  106 . The temperature Tbat [° C.] of the battery  30  (hereinafter referred to as the “battery temperature Tbat” is detected by a temperature sensor  108 , and outputted to the battery ECU  32  through a signal line  110 . 
       (A1-4-2. Battery ECU  32 ) 
       [0059]    The battery ECU  32  controls the battery  30  based on input values such as command values from the management ECU  50 . The battery ECU  32  calculates a remaining capacity of the battery  30  (hereinafter referred to as the “SOC” or the “battery SOC”) based on the BAT terminal voltage Vbat and the BAT terminal current Ibat for use of management of the battery  30 . 
         [0060]    For example, the battery ECU  32  calculates an input limit value Pbatlimin of the battery  30  (hereinafter also referred to as the “BAT terminal input limit value Pbatlimin”) [W] and an output limit value Pbatlimout of the battery  30  (hereinafter also referred to as the “BAT terminal output limit value Pbatlimout”) [W] based on the battery temperature Tbat and SOC. For example, the method of determining (or setting) the input limit value Pbatlimin and the output limit value Pbatlimout is carried out in the same manner as in the case of US 2008/0018111 A1 (see FIGS. 2 and 3 of US 2008/0018111 A1). 
         [0061]    Further, the battery ECU  32  of the first embodiment controls the step-down converter  42  based on input values such as command values from the management ECU  50 . The input terminal voltage [V] of the step-down converter  42  (hereinafter referred to as the “step-down converter terminal voltage Vlow”) is detected by a voltage sensor  120 , and outputted to the battery ECU  32  through a signal line  122 . The input terminal current [A] of the step-down converter  42  (hereinafter referred to as the “step-down converter terminal current Ilow”) is detected by a current sensor  124 , and outputted to the battery ECU  32  through a signal line  126 . The battery ECU  32  calculates step-down converter terminal electric power Plow [W] (hereinafter referred to as the “step-down converter power consumption Plow” or the “power consumption Plow”) by multiplying the step-down converter terminal voltage Vlow by the step-down converter terminal current Ilow. 
         [0062]    The battery ECU  32  sends the BAT terminal voltage Vbat, the BAT terminal current Ibat, the battery temperature Tbat, the battery SOC, the BAT terminal input limit value Pbatlimin, the BAT terminal output limit value Pbatlimout, and the step-down converter terminal electric power Plow to the MG ECU  50 , the FC converter ECU  26 , etc. through the CAN  70 . 
       (A1-4-3. Battery Converter 34) 
       [0063]    The BAT converter  34  is a chopper type step-up/down (voltage boost/buck) converter (DC/DC converter). That is, the BAT converter  34  steps up the output voltage of the battery  30  (BAT terminal voltage Vbat), and supplies the stepped up voltage to the inverter  14 . Further, the BAT converter  34  steps down the regenerative voltage of the motor  12  (hereinafter referred to as the “regenerative voltage Vreg”) or the secondary voltage Vfccon 2  of the FC converter  24 , and supplies the stepped down voltage to the battery  30 . 
         [0064]    The BAT converter  34  is provided between the battery  30  and the inverter  14 . Stated otherwise, one terminal of the BAT converter  34  is connected to the primary side where the battery  30  is present, and the other terminal of the BAT converter  34  is connected to the secondary side as a node between the FC  20  and the inverter  14 . 
         [0065]    The primary voltage Vbatcon 1  of the BAT converter  34  is detected by a voltage sensor  130 , and outputted to the BAT converter ECU  36  through a signal line  132 . The primary current Ibatcon 1  of the BAT converter  34  is detected by a current sensor  134 , and outputted to the BAT converter ECU  36  through a signal line  136 . The secondary current Ibatcon 2  of the BAT converter  34  is detected by a current sensor  138 , and outputted to the BAT converter ECU  36  through a signal line  140 . 
         [0066]    It should be noted that the primary voltage Vbatcon 1  is voltage on the BAT converter  34  side, from a node  144  for auxiliary devices, in a power line  142  connecting the battery  30  and the BAT converter  34 . Likewise, the primary current Ibatcon 1  is current on the BAT converter  34  side, from the node  144  for the auxiliary devices, in the power line  142  connecting the battery  30  and the BAT converter  34 . 
         [0067]    In the case where no auxiliary devices (air pump  28 , etc.) are connected to the power line  142 , one of the voltage sensors  100 ,  130  may be omitted, and one of the current sensors  104 ,  134  may be omitted. 
       (A1-4-4. Battery Converter ECU  36 ) 
       [0068]    The BAT converter ECU  36  controls the BAT converter  34  based on input values such as command values from the management ECU  50 . Hereinafter, the BAT converter  34  and the BAT converter ECU  36  will be referred to as the “BAT VCU  150 ” as having a meaning of a voltage control unit for the battery  30 . 
         [0069]    The BAT converter ECU  36  sends the primary voltage Vbatcon 1 , the primary current Ibatcon 1 , the secondary current Ibatcon 2 , and the passing current Ibatt to the MG ECU  50 , the FC converter ECU  26 , etc. through the CAN  70 . The passing current Ibatt is current passing through the BAT converter  34 . The BAT converter ECU  36  selects one of the primary Ibatcon 1  and the secondary current Ibatcon 2 , outputted from the BAT converter  34  as the passing current Ibatt. For example, when the battery  30  is being charged, the primary current Ibatcon 1  is the passing current Ibatt. 
       (A1-5. Auxiliary Devices) 
       [0070]    As described above, in the first embodiment, the auxiliary devices include, for example, the air pump  28 , the air conditioner  40 , the step-down converter  42  (step down type DC-DC converter) and the 12V system  44 . Additionally, a water pump (not shown) for circulating water as a coolant for cooling the FC  20 , included in the cooling system of the FC system  2000  may also be an auxiliary device. 
         [0071]    The air conditioner  40  regulates the temperature, etc. in the vehicle  10 . The power consumption Pac [W] of the air conditioner  40  is transmitted from a control unit (not shown) of the air conditioner  40  to the MG ECU  50 , the FC converter ECU  26 , etc. through the CAN  70 . 
         [0072]    The step-down converter  42  steps down the voltage on the primary side of the BAT converter  34  (BAT VCU  150 ), and supplies the stepped down voltage to the 12V system  44 . The 12V system  44  includes a 12V battery, accessories, a radiator fan, a head light, etc. (not shown). The accessories include devices such as an audio device and a navigation device. The radiator fan is a fan for cooling a coolant to be circulated by the water pump, in a radiator. 
       (A1-6. Management ECU  50 ) 
       [0073]    The management ECU  50  sends command values to the MOT ECU  16 , the FC ECU  22 , the FC converter ECU  26 , the BAT ECU  32 , and the BAT converter ECU  36 , etc. through the communications network  70  ( FIG. 1 ). In this manner, the motor  12 , the inverter  14 , the FC  20 , the FC converter  24 , the battery  30 , the BAT converter  34 , and the auxiliary devices are controlled. In the control, the MG ECU  50  executes a program stored in a memory unit (not shown). Further, the MG ECU  50  uses detection values of various sensors such as the voltage sensors  60 ,  80 ,  88 ,  100 ,  120 ,  130 , and the current sensors  64 ,  84 ,  92 ,  104 ,  124 ,  134 ,  138 , etc. 
         [0074]    In addition to the above sensors, the various sensors herein include an accelerator pedal operation amount sensor (hereinafter referred to as the “AP operation amount sensor”), a motor rotational number sensor, and a wheel velocity sensor (all of these sensors are not shown). The AP operation amount sensor detects the operation amount [%] of the accelerator pedal (not shown). The motor rotational number sensor detects the rotational number of the motor  12  (hereinafter referred to as the “motor rotation number Nmot” or “rotation number Nmot”) [rpm]. The MG ECU  50  uses the rotational number Nmot to detect the vehicle velocity V [km/h] of the FC vehicle  10 . The wheel velocity sensor detects the velocity of each wheel (wheel velocity), not shown. 
         [0075]    The MG ECU  50  calculates the load required for the entire FC vehicle  10  (entire load), based on inputs from various switches and various sensors (load requirements) in addition to the state of the FC  20 , the state of the battery  30 , and the state of the motor  12 . Further, the MG ECU  50  balances, and determines proportions (assignments) of the load (FC load) to be powered by the FC stack  20  and the load (battery load) to be powered by the battery  30 , and the load (generation load) to be powered by the regenerative power source (motor  12 ). Based on these loads, the MG ECU  50  sends command values to the MOT ECU  16 , the FC ECU  22 , the FC converter ECU  26 , the BAT ECU  32 , the BAT converter ECU  36 , etc. 
         [0076]    The command values transmitted from the MG ECU  50  to the FC converter ECU  26  include a requirement value of primary current Ifccon 1  of the FC converter  24  (hereinafter referred to as the “requirement primary current Ifccon 1 req”). The requirement primary current Ifccon 1 req can be understood as the requirement value of the output current of the FC  20 . Stated otherwise, the requirement primary current Ifccon 1 req is a load to be powered by the FC  20  (i.e., the target output of the FC  20 ). 
       [A2. Control of First Embodiment] 
       [0077]    Next, mainly, control (FC converter control) of the FC converter  24  by the FC converter ECU  26  will be explained. 
       (A2-1. Summary of FC Converter Control) 
       [0078]      FIG. 2  shows a flow chart for controlling the FC converter  24  (FC converter control) by the FC converter ECU  26 , in the first embodiment. In step S 1 , the FC converter ECU  26  updates various sensor values Mdir directly inputted to the FC converter ECU  26 . 
         [0079]    The various sensor values Mdir herein include the FC converter primary voltage Vfccon 1  from the voltage sensor  80 , the FC converter primary current Ifccon 1  from the current sensor  84 , and the FC converter secondary voltage Vfccon 2  from the voltage sensor  88 . Further, in the first embodiment, the current sensor  104  is directly connected to the FC converter ECU  26  ( FIG. 1 ). Therefore, the BAT terminal current Ibat is also included in the sensor values Mdir. 
         [0080]    The updating cycle Tdir of these sensor values Mdir is, e.g., several msec. The updating cycle Tdir may vary for each of the sensor values Mdir. 
         [0081]    In step S 2 , the FC converter ECU  26  updates various control values Ccan and sensor values Mcan inputted through the CAN  70 . The control values Ccan herein include the requirement primary current Ifccon 1 req of the FC converter  24  and the input limit value Pbatlimin and the output limit value Pbatlimout of the battery  30 . Further, the sensor values Mcan herein include the inverter electric power Pinv, the air conditioner power consumption Pac, the air pump power consumption Pap, the stepped down converter power consumption Plow, the BAT terminal voltage Vbat, the primary voltage Vbatcon 1 , the primary current Ibatcon 1 , the secondary current Ibatcon 2 , and the passing current Ibatt of the BAT converter  34 . 
         [0082]    The updating cycle Tcan of these control values Ccan and the sensor values Mcan is, e.g., several tens of msec. The updating cycle Tcan is longer than the updating cycle Tdir of step S 1 . The updating cycle Tdir may vary for each of the control values Ccan or the sensor values Mcan. The computation cycle (hereinafter referred to as the “control cycle Tc”) of the steps S 1  to S 4  in  FIG. 2  in the first embodiment is, e.g., several msec. The control cycle Tc is equal to the updating cycle Tdir of the sensor values Mdir. For example, it may be possible to use the control cycle Tc which is shorter than the updating cycle Tdir or longer than the updating cycle Tdir, from the viewpoint of making the updating cycle Tdir and the control cycle Tc shorter than the updating cycle Tcan. 
         [0083]    In step S 3 , the FC converter ECU  26  calculates the target primary current Ifccon 1 tar of the FC converter  24  based on the control values Ccan and the sensor values Mdir, Mcan (Detailed explanation will be given later with reference to  FIGS. 3 to 6 .). 
         [0084]    In step S 4 , the ECU  26  controls the FC converter  24  for realizing the target primary current Ifccon 1 tar calculated in step S 3 . Specifically, in the case where the primary current Ifccon 1  is smaller than the target primary current Ifccon 1 tar, the drive duty ratio for the FC converter  24  is increased. In the case where the primary current Ifccon 1  is larger than the target primary current Ifccon 1 tar, the drive duty ratio for the FC converter  24  is decreased. In the case where the primary current Ifccon 1  is equal to the target primary current Ifccon 1 tar, the present drive duty ratio for the FC converter  24  is maintained. 
       (A2-2. Calculation of the Target Primary Current Ifccon 1 tar of the FC Converter  24  (S 3  of FIG.  2 )) 
     (A2-2-1. Overall Flow of Calculation of the Target Primary Current Ifccon 1 tar) 
       [0085]      FIG. 3  is a diagram illustrating calculation of the target primary current Ifccon 1 tar of the FC converter  24  in the first embodiment.  FIG. 4  is a flow chart for calculating the target primary current Ifccon 1 tar of the FC converter  24  (details of S 3  of  FIG. 2 ), in the first embodiment. Each of  FIGS. 3 and 4  shows the procedure at the time of charging the battery  30 . 
         [0086]    In  FIG. 3 , items in ovals denote the control values Ccan or the sensor values Mdir, Mcan. In particular, the items in bold ovals are the sensor values Mdir (values directly inputted to the FC converter ECU  26 ). The items in non-bold ovals denote the control values Ccan or the sensor values Mcan (values inputted to the FC converter ECU  26  through the CAN  70 ). Further, the items in blocks  200 ,  202 ,  204 ,  206 ,  210 ,  212 ,  214  in  FIG. 3  (hereinafter referred to as the “computation blocks  200 ,  202 ,  204 ,  206 ,  210 ,  212 ,  214 ” or the blocks  200 ,  202 ,  204 ,  206 ,  210 ,  212 ,  214 ″), and an adder  208  show processes in the FC converter ECU  26 . 
         [0087]    In the computation block  200  of  FIG. 3  (step S 11  of  FIG. 4 ), the FC converter ECU  26  calculates the primary current limit value Ifccon 1 lim 1  of the FC converter  24  from the viewpoint of protecting the battery  30 . The detailed explanation will be given later with reference to  FIG. 5 . 
         [0088]    In the computation block  202  of  FIG. 3  (step S 12  of  FIG. 4 ), the FC converter ECU  26  calculates the primary current limit value Ifccon 1 lim 2  of the FC converter  24  from the viewpoint of protecting the FC converter  24 , based on the input limit value Pbatlimin and the BAT terminal voltage Vbat of the battery  30 . For example, the ECU  26  calculates the primary current limit value Ifccon 1 lim 2  by dividing the input limit value Pbatlimin by the BAT terminal voltage Vbat. 
         [0089]    In the computation block  204  of  FIG. 3  (step S 13  of  FIG. 4 ), the ECU  26  selects the smallest value among the requirement primary current Ifccon 1 req from the MG ECU  50  and the primary current limit values Ifccon 1 lim 1 , Ifccon 1 lim 1  calculated in the computation blocks  200 ,  202  (steps S 11 , S 12 ) as a provisional target primary current Ifccon 1 tarp. Therefore, the requirement primary current Ifccon 1 req is limited by this selection. 
         [0090]    In the computation block  206  of  FIG. 3  (step S 14  of  FIG. 4 ), the ECU  26  calculates a feedback correction value ΔIfccon 1 cor of the primary current Ifccon 1  of the FC converter  24  (hereinafter referred to as the “F/B correction value ΔIfccon 1 cor”). The detailed explanation will be given later with reference to  FIG. 6 . 
         [0091]    In the adder  208  of  FIG. 3  (step S 15  of  FIG. 4 ), the FC converter ECU  26  calculates a target primary current Ifccon 1 tar by adding the F/B correction value ΔIfccon 1 cor calculated in the computation block  206  (S 14  of  FIG. 4 ) to the provisional target primary current Ifccon 1 tarp calculated in the computation block  204  (S 13  of  FIG. 4 ). 
       (A2-2-2. Calculation of Primary Current Limit Value Ifccon 1 lim 1 ) 
       [0092]      FIG. 5  is a flow chart (details of S 11  in  FIG. 4 ) for calculating a primary current limit value Ifccon 1 lim 1  of the FC converter  24  from a viewpoint of protecting the battery  30 , in the first embodiment. In step S 21  of  FIG. 5  (computation block  210  of  FIG. 3 ), the FC converter ECU  26  adds up the air pump power consumption Pap, the air conditioner power consumption Pac, and the power consumption Plow of the step-down converter  42  to calculate the auxiliary device power consumption Paux. All of the power consumption Pap, the power consumption Pac, and the power consumption Plow are sensor values Mcan obtained by the FC converter  24  through the CAN  70 . 
         [0093]    In step S 22  of  FIG. 5  (computation block  212  of  FIG. 3 ), the ECU  26  calculates the estimated power consumption Lbatcon of the BAT converter  34  based on the passing current Ibatt and the primary voltage Vbatcon 1  of the BAT converter  34 , and the secondary voltage Vfccon 2  of the FC converter  24 . Specifically, a map defining the relationship between the estimated power consumption Lbatcon and the combination of the passing current Ibatt, the primary voltage Vbatcon 1 , and the secondary voltage Vfccon 2  is stored in a memory unit of the FC converter ECU  26  beforehand. Further, the FC converter ECU  26  identifies the estimated power consumption Lbatcon based on the combination of the passing current Ibatt, the primary voltage Vbatcon 1 , and the secondary voltage Vfccon 2 . 
         [0094]    The passing current Ibatt and the primary voltage Vbatcon 1  are sensor values Mcan obtained through the CAN  70 . The secondary voltage Vfccon 2  is a sensor value Mdir obtained by the FC converter ECU  26  directly from the voltage sensor  88 . Therefore, at the time of repeating the steps S 21  to S 24  in  FIG. 5 , the passing current Ibatt and the primary voltage Vbatcon 1  are updated at the updating cycle Tcan, and the secondary voltage Vfccon 2  is updated at the control cycle Tc (=updating cycle Tdir&lt;Tcan). 
         [0095]    In step S 23  of  FIG. 5  (computation block  200  of  FIG. 3 ), the FC converter ECU  26  subtracts the BAT terminal input limit value Pbatlimin from the inverter electric power Pinv, and adds a control margin Pmar, the auxiliary power consumption Paux and the estimated power consumption Lbatcon to the inverter electric power Pinv to calculate an electric power limit value Pfccon 1 im of the FC converter  24 . The inverter electric power Pinv and the BAT terminal input limit value Pbatlimin are the sensor value Mcan and control value Ccan obtained by the FC converter  24  through the CAN  70 . The control margin Pmar is a memory value stored in the memory unit of the FC converter ECU  26 . The estimated power consumption Lbatcon is a value calculated in the computation block  212  (S 22  in  FIG. 5 ). 
         [0096]    In step S 24  of  FIG. 5  (computation block  200  of  FIG. 3 ), the FC converter ECU  26  divides the electric power limit value Pfccon 1 im calculated in step S 23  by the primary voltage Vfccon 1  of the FC converter  24  to calculate the primary current limit value Ifccon 1 lim 1 . The primary voltage Vfccon 1  is a sensor value Mdir obtained by the FC converter ECU  26  directly from the voltage sensor  80 . 
       (A2-2-3. Calculation of the F/B Correction Value ΔIfccon 1 cor) 
       [0097]      FIG. 6  is a flow chart (details of S 14  of  FIG. 4 ) for calculating a F/B correction value ΔIfccon 1 cor of the primary current Ifccon 1  of the FC converter  24 , in the first embodiment. In step S 31  of  FIG. 6  (computation block  214  of  FIG. 3 ), the FC converter ECU  26  multiplies the BAT terminal voltage Vbat by the BAT terminal current Ibat to calculate the BAT terminal electric power Pbat. 
         [0098]    As described above, in the first embodiment, the BAT terminal voltage Vbat from the voltage sensor  100  is inputted to the FC converter ECU  26  through the CAN  70 , and the BAT terminal current Ibat from the current sensor  104  is directly inputted to the FC converter ECU  26  ( FIG. 1 ). Therefore, the BAT terminal voltage Vbat is a sensor value Mcan obtained by the FC converter ECU  26  through the CAN  70 , and the BAT terminal current Ibat is a sensor value Mdir obtained by the FC converter ECU  26  directly from the current sensor  104 . Therefore, the BAT terminal voltage Vbat is updated at the updating cycle Tcan, and the BAT terminal current Ibat is updated at the updating cycle Tdir (&lt;Tcan). 
         [0099]    In step S 32  of  FIG. 6  (computation block  206  of  FIG. 3 ), the FC converter ECU  26  subtracts the BAT terminal input limit value Pbatlimin from the BAT terminal electric power Pbat, and adds the control margin Pmar to the BAT terminal electric power Pbat, to calculate a deviation ΔPbat. The BAT terminal electric power Pbat is computed in the computation block  214  (S 31  of  FIG. 6 ). The BAT terminal input limit value Pbatlimin is a sensor value Mcan obtained by the FC converter  24  through the CAN  70 . Further, the control margin Pmar is a memory value stored in the memory unit of the FC converter ECU  26 . Since the BAT terminal electric power Pbat is computed at the control cycle Tc (&lt;updating cycle Tcan), the deviation ΔPbat is also computed at the control cycle Tc (&lt;updating cycle Tcan). 
         [0100]    In step S 33  of  FIG. 6  (computation block  206  in  FIG. 3 ), the FC converter ECU  26  implements PID control (PID: Proportional Integral Derivative) based on the deviation ΔPbat calculated in step S 32  to calculates the F/B correction value ΔIfccon 1 cor. 
       [A3. Advantages of First Embodiment] 
       [0101]    As described above, in the first embodiment, the FC converter ECU  26  (part of power generation control unit) uses the requirement primary current Ifccon 1 req (power generation command value of the FC  20  (power generation device)) obtained from the MG ECU  50  (power generation management unit) through the CAN  70  (first signal system) and the BAT terminal current Ibat (parameter) obtained from the current sensor  104  (parameter acquisition unit) through the signal line  106  (second signal system) ( FIG. 1 ) to control the FC  20 . Therefore, for example, in the normal state, the requirement primary current Ifccon 1 req is used mainly, and if an instantaneous change occurs in the BAT terminal current Ibat, etc. regarding inputs to, or outputs from the battery  30  (energy storage device) (e.g., rapid increase in the input electric power to the battery  30  resulting from rapid decrease in the power consumption of the drive motor  12  due to locking of the wheels, etc.), by focusing on the change of the BAT terminal current Ibat, etc., it becomes possible to control power generation of the battery  30 . Therefore, it becomes possible to protect the battery  30  responsive to the rapid change in the input to, or output from the battery  30 . 
         [0102]    In the first embodiment, the FC converter ECU  26  (part of the power generation control unit) corrects the requirement primary current Ifccon 1 req (power generation command value of the FC  20  (power generation device)) obtained from the MG ECU  50  (power management unit) through the CAN  70  (first signal system) using the BAT terminal current Ibat (parameter) ( FIG. 1 ) obtained from the current sensor  104  (parameter acquisition unit) through the signal line  106  (second signal system) to control the FC  20  (power generation device ( FIGS. 3 and 6 , etc.). In this manner, it becomes possible to protect the battery  30  by avoiding the rapid change in the input to or the output from the battery  30  (energy storage device). 
         [0103]    For example, a rapid increase in the input electric power to the battery  30  (energy storage device) resulting from a rapid decrease in the power consumption of the drive motor  12  by locking of the wheels may be regarded as a cause of the change in the instantaneous change in the BAT terminal current Ibat. Additionally, changes in the output of the air pump  28  and ripple noises may be the causes the instantaneous change in the BAT terminal current Ibat. 
         [0104]    In the first embodiment, the FC converter ECU  26  (part of the power generation control unit obtains the requirement primary current Ifccon 1 req from the MG ECU  50  (power management unit) through the CAN  70  (first signal system) at the updating cycle Tcan (first cycle) (S 2  of  FIG. 2 ). Further, the ECU  26  obtains the BAT terminal current Ibat (parameter) from the current sensor  104  (parameter acquisition unit) through the signal line  106  (second signal system) at the updating cycle Tdir (second cycle) which is shorter than the updating cycle Tcan (S 1  of  FIG. 2 ). Then, the ECU  26  implements control of the FC  20  using the requirement primary current Ifccon 1 req (target primary current Ifccon 1 tar) corrected using the BAT terminal current Ibat, etc., at the control cycle Tc (third cycle) which is shorter than the updating cycle Tcan. 
         [0105]    In the first embodiment as described above, the FC converter ECU  26  corrects the requirement primary current Ifccon 1 req obtained from the MG ECU  50  through the CAN  70  using the BAT terminal current Ibat, etc. obtained directly from the current sensor  104  through the signal line  106  to control the FC  20  ( FIGS. 6 and 3 , etc.). Further, the updating cycle Tdir for obtaining the BAT terminal current Ibat and the control cycle Tc (third cycle) of the FC  20  are shorter than the updating cycle Tcan for obtaining the requirement primary current Ifccon 1 req. Therefore, it becomes possible to control power generation of the battery  30  responsive to the instantaneous change in the BAT terminal current Ibat (e.g., rapid increase in the input electric power to the battery  30  resulting from rapid decrease in the power consumption of the drive motor  12  due to locking of the wheels, etc.). Therefore, by avoiding the rapid charge in the input to or the output from the battery  30 , it becomes possible to protect the battery  30 . 
         [0106]    In the first embodiment, when the requirement primary current Ifccon 1 req obtained from the MG ECU  50  exceeds the primary current limit value Ifccon 1 lim 1  or Ifccon 1 lim 2 , the FC converter ECU  26  (part of the power generation control unit) selects the primary current control value Ifccon 1 lim 1  or Ifccon 1 lim 2  as the target primary current Ifccon 1 tar (block  204  in  FIG. 3  and S 13  in  FIG. 4 ). Stated otherwise, when the input electric power to the battery  30  (energy storage device) exceeds the input electric power threshold value, the FC converter ECU  26  limits the output of the FC  20 . In this manner, the input electric power to the battery  30  is decreased, and overcharging of the battery  30  is avoided. Thus, it becomes possible to protect the battery  30 . 
         [0107]    In the first embodiment, the FC VCU  96  (power generation control unit) includes the FC converter  24  (first converter) on the FC  20  side, and the FC converter ECU  26  (first converter control unit) for controlling the FC converter  24  ( FIG. 1 ). Further, the vehicle  10  (power system) includes the BAT converter  34  (second converter) on the battery  30  (energy storage device) side, and the BAT converter ECU  36  (second converter control unit) for controlling the BAT converter  34  ( FIG. 1 ). 
         [0108]    Further, when the requirement primary current Ifccon 1 req obtained from the MG ECU  50  exceeds the primary current limit value Ifccon 1 lim 1  (or Ifccon 1 lim 2 ), the FC converter ECU  26  selects the primary current limit value Ifccon 1 lim 1  (or Ifccon 1 lim 2 ) as the target primary current Ifccon 1 tar (block  204  in  FIG. 3 , S 13  in  FIG. 4 ). Stated otherwise, when the input electric power to the battery  30  exceeds the input electric power threshold value, the FC converter ECU  26  limits the output current of the FC  20 , and changes the primary current limit value Ifccon 1 lim 1  (or Ifccon 1 lim 2 ) (output current limit value) of the FC converter  24  ( FIG. 5 ) based on the input electric power threshold value of the battery  30 . In this manner, it becomes possible to impose a suitable limitation to the output current of the FC  20  in correspondence with the input electric power threshold value of the battery  30 . 
         [0109]    In the first embodiment, the primary current limit value Ifccon 1 lim 2  of the FC converter  24  (input electric power threshold value of the battery  30  (energy storage device) is determined based on the battery temperature Tbat and SOC. Thus, it becomes possible to suitably determine the primary current limit value Ifccon 1 lim 2 , and moreover, impose a suitable limitation to the output current of the FC  20 . 
         [0110]    In the first embodiment, the FC converter ECU  26  (first converter control unit) corrects the output of the FC  20  based on the deviation ΔPbat between the BAT terminal electric power Pbat (input electric power of the energy storage device) and the BAT terminal input limit value Pbatlimin (input electric power threshold value) ( FIGS. 6, 3 , etc.). Thus, based on the deviation ΔPbat, it becomes possible to suitably correct the output of the FC  20 . 
       B. Second Embodiment 
       [0111]    [B1. Structure of the Second Embodiment (Difference from First Embodiment)] 
         [0112]      FIG. 7  is a diagram schematically showing overall structure of a fuel cell vehicle  10 A (hereinafter referred to as the “FC vehicle  10 A” or the “vehicle  10 A”) as an electric power system according to a second embodiment of the present invention. The constituent elements that are identical to those of the first embodiment are labeled with the same reference numerals, and description thereof will be omitted. 
         [0113]    In the vehicle  10  of the first embodiment, the current sensor  104  is connected to the FC converter ECU  26  through the signal line  106 , and the BAT terminal current Ibat is directly inputted to the ECU  26  ( FIG. 1 ). In contrast, in the vehicle  10 A of the second embodiment, the current sensor  134  is connected to the FC converter electronic control unit  26   a  (hereinafter referred to as the “FC converter ECU  26   a ”or the “ECU  26   a ”) through the signal line  136 , and the primary current Ibatcon 1  of the BAT converter  34  is directly inputted to the ECU  26   a  ( FIG. 7 ). 
         [0114]    Further, in the FC converter ECU  26  of the first embodiment, the BAT terminal electric power Pbat calculated based on the BAT terminal voltage Vbat and the BAT terminal current Ibat is used (computation block  214  in  FIG. 3  and S 31  of  FIG. 6 ). In contrast, in the FC converter ECU  26   a  of the second embodiment, estimated BAT terminal electric power Pbatest estimated based on the primary voltage Vbatcon 1  and the primary current Ibatcon 1 , etc. of the BAT converter  34  is used (computation block  214   a  of  FIG. 8  and S 43  of  FIG. 9 ). 
       [B2. Control of Second Embodiment] 
     (B2-1. Summary of FC Converter Control) 
       [0115]    The summary of the control (FC converter control) of the FC converter  24  by the FC converter ECU  26   a  in the second embodiment is the same as that of the first embodiment ( FIG. 2 ). 
         [0116]    However, as described above, in the second embodiment, the current sensor  134  is connected to the FC converter ECU  26   a  through the signal line  136 , and the primary current Ibatcon 1  of the BAT converter  34  is directly inputted to the ECU  26   a  ( FIG. 7 ). Therefore, in the case of the second embodiment, the various sensor values Mdir directly inputted to the ECU  26   a  in step S 1  of  FIG. 2  include the primary current Ibatcon 1 , and do not include the BAT terminal current Ibat. Further, the various sensor values Mcan directly inputted to the ECU  26   a  through the CAN  70  in step S 2  of  FIG. 2  include the BAT terminal current Ibat, and do not include primary current Ibatcon 1 . 
         [0117]    Also in the second embodiment, the updating cycle Tdir in step S 1  of  FIG. 2  is shorter than the updating cycle Tcan in step S 2 . 
       (B2-2. Calculation of Target Primary Current Ifccon 1 tar of the FC Converter  24  (S 3  of FIG.  2 )) 
     (B2-2-1. Overall Flow of Calculation of Target Primary Current Ifccon 1 tar) 
       [0118]      FIG. 8  is a view showing calculation of the target primary current Ifccon 1 tar of the FC converter  24  according to the second embodiment. The summary of the flow chart (details of S 3  of  FIG. 2 ) for calculating the target primary current Ifccon 1 tar of the FC converter  24  is the same as that of the first embodiment ( FIG. 4 ). Further, the summary of calculation of the primary current limit value Ifccon 1 lim 1  of the FC converter  24  (S 11  of  FIG. 4 ) from the viewpoint of protecting the battery  30  is the same as that of the first embodiment ( FIG. 5 ). As for the difference between  FIG. 3  of the first embodiment and  FIG. 8  of the second embodiment, explanation will be given later with reference to  FIG. 9 . 
       (B2-2-2. Calculation of F/B Correction Value ΔIfccon 1 cor) 
       [0119]      FIG. 9  is a flow chart for calculating an F/B correction value ΔIfccon 1 cor of the Ifccon 1  of the FC converter  24  (details of S 14  of  FIG. 4 ) in the second embodiment. In step S 41  of  FIG. 9  (computation block  220  of  FIG. 8 ), the FC converter ECU  26   a  multiplies the primary voltage Vbatcon 1  of the BAT converter  34  by the primary current Ibatcon 1  of the BAT converter  34  to calculate the primary electric power Pbatcon 1 . 
         [0120]    As described above, in the second embodiment, the primary voltage Vbatcon 1  from the voltage sensor  130  is inputted to the ECU  26   a  through the CAN  70 , and the primary current Ibatcon 1  from the current sensor  134  is directly inputted to the ECU  26   a  ( FIG. 7 ). Therefore, the primary voltage Vbatcon 1  is a sensor value Mcan obtained by the ECU  26   a  through the CAN  70 , and the primary current Ibatcon 1  is a sensor value Mdir obtained by the ECU  26   a  directly from the current sensor  134 . Thus, the primary voltage Vbatcon 1  is updated at the updating cycle Tcan, and the primary current Ibatcon 1  is updated at the updating cycle Tdir (&lt;Tcan). 
         [0121]    In step S 42  of  FIG. 9  (computation block  214   a  of  FIG. 8 ), the FC converter ECU  26   a  obtains the auxiliary device power consumption Paux calculated in step S 21  of  FIG. 5  (computation block  210  of  FIG. 8 ). 
         [0122]    In step S 43  (computation block  214   a  of  FIG. 8 ), the ECU  26   a  adds up the primary electric power Pbatcon 1  of the BAT converter  34  and the auxiliary device power consumption Paux to calculate the estimated BAT terminal electric power Pbatest. 
         [0123]    In step S 44  (computation block  206   a  of  FIG. 8 ) of  FIG. 9 , the FC converter ECU  26   a  subtracts the BAT terminal input limit value Pbatlimin from the estimated BAT terminal electric power Pbatest, and then, add a control margin Pmar to the estimated BAT terminal electric power Pbatest, to calculate the deviation ΔPbat 2 . The estimated BAT terminal electric power Pbatest is computed in the computation block  214   a  (S 43  of  FIG. 9 ). The BAT terminal input limit value Pbatlimin is a sensor value Mcan obtained by the FC converter  24  through the CAN  70 . Further, the control margin Pmar is a memory value stored in the memory unit of the FC converter ECU  26   a.  Since the estimated BAT terminal electric power Pbatest is computed by the control cycle Tc (&lt;updating cycle Tcan), the deviation ΔPbat 2  is also computed by the control cycle Tc (&lt;updating cycle Tcan). 
         [0124]    In step S 45  of  FIG. 9  (computation block  206   a  of  FIG. 8 ), the FC converter ECU  26   a  implements PID control based on the deviation ΔPbat 2  calculated in step S 44  to calculate the F/B correction value ΔIfccon 1 cor. 
       [B3. Second Embodiment and Comparative Example] 
       [0125]      FIG. 10  is a time chart showing various sensor values Mdir, Mcan, and control values Ccan in a fuel cell vehicle according to a comparative example.  FIG. 11  is a time chart showing the various sensor values Mdir, Mcan and control values Ccan in the FC vehicle  10 A according to the second embodiment. In the comparative example of  FIG. 10 , the primary current Ibatcon 1  from the current sensor  134  is not directly inputted to the FC converter ECU  26   a,  but inputted to the FC converter ECU  26   a  through the CAN  70 . 
         [0126]    The wheel velocity Vw [km/h] is shown at the uppermost charts of  FIGS. 10 and 11 . The second charts from the top of  FIG. 10  and  FIG. 11  show the FC terminal electric power Pfc [W], the BAT terminal electric power Pbat [W], the estimated BAT terminal electric power Pbatest [W], and the inverter electric power Pinv [W] at the time of transmission by the MG ECU  50 . Additionally, in  FIG. 10 , the inverter electric power Pinv [W] at the time of reception by the FC converter ECU  26   a  is shown. 
         [0127]    The BAT terminal electric power Pbat [W] is shown at the third charts from the top of  FIGS. 10 and 11 . The BAT terminal electric power Pbat at the third charts is an enlargement of the BAT terminal electric power Pbat at the second charts. Both represent the same data. Further, as can be seen from the positions of the BAT terminal input limit value Pbatlimin and the BAT terminal output limit value Pbatlimout, it should be noted that in the third charts the scale of the BAT terminal electric power Pbat in  FIG. 10  is different from the scale in  FIG. 11  in the vertical direction. 
         [0128]    At the fourth charts from the top of  FIGS. 10 and 11 , the primary current Ifccon 1  [A] of the FC converter  24 , the requirement primary current Ifccon 1 req [A] at the time of transmission by the MG ECU  50 , the requirement primary current Ifccon 1 req [A] at the time of reception by the FC converter ECU  26   a,  and the target primary current Ifccon 1 tar [A] are shown. In the fourth charts of  FIGS. 10 and 11 , the primary current Ifccon 1  matches the target primary current Ifccon 1 tar. This is because, in the comparative example, when the primary current Ifccon 1  is decreased, the target primary current Ifccon 1 tar is not more than the primary current Ifccon 1 . 
         [0129]    At the time point t 1  of  FIGS. 10 and 11 , a hydraulic braking mechanism (not shown) is operated to lock the wheels (not shown). After the time point t 1 , as a result of the rapid decrease in the wheel velocity Vw, the BAT terminal electric power Pbat is switched from the discharging state to the charging state. 
         [0130]    At this time, in comparison with the comparative example, in the second embodiment, decrease in the target primary current Ifccon 1 tar is started at an early stage. That is, in the comparative example, the target primary current Ifccon 1 tar is decreased from the time point t 3 . In contrast, in the second embodiment, the target primary current Ifccon 1 tar is decreased from the time point t 2 . 
         [0131]    At the time of calculating the target primary current Ifccon 1 tar (BAT converter primary electric power Pbatcon 1 ), the primary voltage Vbatcon 1  of the BAT converter  34  is used (computation block  220  of  FIG. 8  and S 41  of  FIG. 9 ). Further, in the second embodiment, the primary current Ibatcon 1  is directly inputted from the current sensor  134  to the FC converter ECU  26   a  ( FIG. 7 ). Therefore, in response to the change (decrease) in the primary current Ibatcon 1 , the FC converter ECU  26   a  of the second embodiment can promptly start to decrease the target primary current Ifccon 1 tar. In contrast, in the comparative example, the primary current Ibatcon 1  is inputted to the FC converter ECU  26   a  through the CAN  70 . Therefore, since there is a time difference D to the time when the primary current Ibatcon 1  is inputted to the FC converter ECU  26   a,  it is not possible to promptly start to decrease the target primary current Ifccon 1 tar. 
         [0132]    Since the primary current Ibatcon 1  is handled in a different manner as described above, in comparison with the comparative example, in the second embodiment, excessive decrease in the BAT terminal electric power Pbat can be suppressed. That is, though the BAT terminal electric power Pbat of the second embodiment merely exceeds (or falls short of) the BAT terminal input limit value Pbatlimin slightly, the BAT terminal electric power Pbat of the comparative example exceeds (or falls short of) the BAT terminal input limit value Pbatlimin significantly. 
       [B4. Advantages of Second Embodiment] 
       [0133]    In the above second embodiment, the following advantages are offered in addition to, or instead of the advantages of the first embodiment. 
         [0134]    In the second embodiment, as the load which is different from the drive motor  12 , auxiliary devices such as the air pump  28  are connected to the power line  142  connecting the battery  30  (energy storage device) and the BAT converter  34  (second converter) ( FIG. 7 ). Further, the FC converter ECU  26   a  (first converter control unit) estimates the input electric power to the battery  30  or the output electric power from the battery  30  based on the primary electric power Pbatcon 1  of the BAT converter  34  (see  FIG. 9 ). In this manner, it becomes possible to monitor the state of the battery  30 . Accordingly, it becomes possible to determine the design more freely, and excellent failsafe characteristics are achieved. 
       C. Third Embodiment 
     [C1. Structure of the Third Embodiment (Difference From First and Second Embodiments)] 
       [0135]      FIG. 12  is a diagram schematically showing overall structure of a fuel cell vehicle  10 B (hereinafter referred to as the “FC vehicle  10 B” or the “vehicle  10 B”) as an electric power system according to a third embodiment of the present invention. The constituent elements that are identical to those of the first and second embodiments are labeled with the same reference numerals, and description thereof will be omitted. 
         [0136]    In the vehicle  10  of the first embodiment, the current sensor  104  is connected to the FC converter ECU  26  through the signal line  106 , and the BAT terminal current Ibat is directly inputted to the FC converter ECU  26  ( FIG. 1 ). In the vehicle  10 A of the second embodiment, the current sensor  134  is connected to the FC converter ECU  26   a  through the signal line  136 , and the primary current Ibatcon 1  of the BAT converter  34  is directly inputted to the FC converter ECU  26   a  ( FIG. 7 ). In contrast, in the vehicle  10 B of the third embodiment, the current sensor  138  is connected to the FC converter electronic control unit  26   b  (hereinafter referred to as the “FC converter ECU  26   b ” or the “ECU  26   b ”) through the signal line  140 , and the secondary current Ibatcon 2  of the BAT converter  34  is directly inputted to the FC converter ECU  26   b  ( FIG. 12 ). 
         [0137]    Further, in the FC converter ECU  26  of the first embodiment, the BAT terminal electric power Pbat calculated based on the BAT terminal voltage Vbat and the BAT terminal current Ibat is used (computation block  214  in  FIG. 3  and S 31  of  FIG. 6 ). In the FC converter ECU  26   a  of the second embodiment, estimated BAT terminal electric power Pbatest estimated based on the primary voltage Vbatcon 1  and the primary current Ibatcon 1 , etc. of the BAT converter  34  is used (computation blocks  214   a,    220  of  FIG. 8  and S 41  to S 43  of  FIG. 9 ). In contrast, in the FC converter ECU  26   b  of the third embodiment, estimated BAT terminal electric power Pbatest 2  estimated based on the secondary voltage Vfccon 2  of the FC converter  24  (which is substantially equal to the secondary voltage of the BAT converter  34 ) and the secondary current Ibatcon 2  of the BAT converter  34 , etc. is used. 
       [C2. Control of Third Embodiment] 
     (C2-1. Summary of FC Converter Control) 
       [0138]    The summary of the control (FC converter control) of the FC converter  24  by the FC converter ECU  26   b  in the third embodiment is the same as that of the first and second embodiments ( FIG. 2 ). 
         [0139]    As described above, in the third embodiment, the current sensor  138  is connected to the FC converter ECU  26   b  through the signal line  140 , and the secondary current Ibatcon 2  of the BAT converter  34  is directly inputted to the FC converter ECU  26   b  ( FIG. 12 ). Therefore, in the case of the third embodiment, the various sensor values Mdir directly inputted to the FC converter ECU  26   b  in step S 1  of  FIG. 2  include the secondary current Ibatcon 2 , and do not include the BAT terminal current Ibat and the primary current Ibatcon 1 . Further, the various sensor values Mcan directly inputted to the FC converter ECU  26   b  through the CAN  70  in step S 2  of  FIG. 2  include the BAT terminal current Ibat and the primary current Ibatcon 1 , and do not include the secondary current Ibatcon 2 . 
         [0140]    Also in the third embodiment, the updating cycle Tdir in step S 1  of  FIG. 2  is shorter than the updating cycle Tcan in step S 2 . 
       (C2-2. Calculation of Target Primary Current Ifccon 1 tar of the FC Converter  24  (S 3  of FIG.  2 )) 
     (C2-2-1. Overall Flow of Calculation of Target Primary Current Ifccon 1 tar) 
       [0141]      FIG. 13  is a diagram illustrating calculation of target primary current Ifccon 1 tar of the FC converter  24  in the third embodiment. The summary of the flow chart (details of S 3  of  FIG. 2 ) of calculating the target primary current Ifccon 1 tar of the FC converter  24  in the third embodiment is the same as those of the first and second embodiments ( FIG. 4 ). Further, the summary of calculation of the primary current limit value Ifccon 1 lim 1  of the FC converter  24  (S 11  of  FIG. 4 ) from the viewpoint of protecting the battery  30  is the same as those of the first and second embodiments ( FIG. 5 ). As for the difference between the  FIG. 13  of the third embodiment from  FIG. 3  of the first embodiment and  FIG. 8  of the second embodiment, explanation will be given later with reference to  FIG. 14 . 
       (C2-2-2. Calculation of F/B Correction Value ΔIfccon 1 cor) 
       [0142]      FIG. 14  is a flow chart for calculating the F/B correction value ΔIfccon 1 cor of the primary current Ifccon 1  of the FC converter  24  (details of S 14  of  FIG. 4 ), in the third embodiment. In step S 51  of  FIG. 14  (computation block  220   a  of  FIG. 13 ), the FC converter ECU  26   b  multiplies the secondary voltage Vfccon 2  of the FC converter  24  by the secondary current Ibatcon 2  of the BAT converter  34  to calculate the secondary electric power Pbatcon 2  of the BAT converter  34 . 
         [0143]    As described above, in the third embodiment, the secondary voltage Vfccon 2  from the voltage sensor  88  and the secondary current Ibatcon 2  from the current sensor  138  are directly inputted to the FC converter ECU  26   b  ( FIG. 12 ). Therefore, the secondary voltage Vfccon 2  and the secondary current Ibatcon 2  are sensor values Mdir directly obtained from the voltage sensor  88  and the current sensor  138  by the FC converter ECU  26   b.  Thus, the secondary voltage Vfccon 2  and the secondary current Ibatcon 2  are updated at the updating cycle Tdir. 
         [0144]    In step S 52  of  FIG. 14  (computation block  214   b  of  FIG. 13 ), the FC converter ECU  26   b  obtains the auxiliary power consumption Paux calculated in step S 21  of  FIG. 5  (computation block  210  of  FIG. 13 ). 
         [0145]    In step S 53  (computation block  214   b  of  FIG. 13 ), the ECU  26   b  adds up the secondary electric power Pbatcon 2  of the BAT converter  34  and the auxiliary device power consumption Paux to calculate the estimated BAT terminal electric power Pbatest 2 . 
         [0146]    In step S 54  (computation block  206   b  of  FIG. 13 ) of  FIG. 14 , the ECU  26   b  subtracts the BAT terminal input limit value Pbatlimin from the estimated BAT terminal electric power Pbatest 2 , and then, add a control margin Pmar to the estimated BAT terminal electric power Pbatest 2 , to calculate the deviation ΔPbat 3 . The estimated BAT terminal electric power Pbatest 2  is computed in the computation block  214   b  (S 53  of  FIG. 14 ). The BAT terminal input limit value Pbatlimin is a sensor value Mcan obtained by the FC converter  24  through the CAN  70 . Further, the control margin Pmar is a memory value stored in the memory unit of the FC converter ECU  26   b.  Since the estimated BAT terminal electric power Pbatest 2  is computed at the control cycle Tc (&lt;updating cycle Tcan), the deviation ΔPbat 3  is also computed at the control cycle Tc (&lt;updating cycle Tcan). 
         [0147]    In step S 55  of  FIG. 14  (computation block  206   b  of  FIG. 13 ), the FC converter ECU  26   b  implements PID control based on the deviation ΔPbat 3  calculated in step S 54  to calculate the F/B correction value ΔIfccon 1 cor. 
       [C 3 . Advantages of Third Embodiment] 
       [0148]    In the third embodiment, in addition to the advantages of the first and second embodiments, the following advantages are obtained. 
         [0149]    In the third embodiment, the FC converter ECU  26   b  (first converter control unit) estimates the input electric power to the battery  30  (energy storage device) or the output electric power from the battery  30  based on the secondary electric power Pbatcon 2  of the BAT converter  34  (second converter) (see  FIG. 14 ). In this manner, it becomes possible to monitor the state of the battery  30 . Accordingly, it becomes possible to determine the design more freely, and excellent failsafe characteristics are achieved. 
         [0150]    Also in the third embodiment, the same waveform as in the case of  FIG. 11  can be obtained. 
       D. Fourth Embodiment 
       [0151]    [D1. Structure of Fourth Embodiment (Difference from First to Third Embodiments)] 
         [0152]      FIG. 15  is a diagram schematically showing overall structure of a fuel cell vehicle  10 C (hereinafter referred to as the “FC vehicle  10 C” or the “vehicle  10 C”) as an electric power system according to a fourth embodiment of the present invention. The constituent elements that are identical to those of the first to third embodiments are labeled with the same reference numerals, and description thereof will be omitted. 
         [0153]    In the vehicles  10 ,  10 A, and  10 B of the first to third embodiments, by implementing the control with the FC converter ECUs  26 ,  26   a,    26   b,  protection of the battery  30  is achieved. In contrast, in the vehicle  10 C according to the fourth embodiment, by implementing the control with the FC converter electronic control unit  26   c  (hereinafter referred to as the “FC converter ECU  26   c ” or the “ECU  26   c ”), and the motor electronic control unit  16   a  (hereinafter referred to as the “motor ECU  16   a ” or the “ECU  16   a ”), protection of the battery  30  is achieved. As shown in  FIG. 15 , the current sensor  104  is connected to the FC converter ECU  26   c  and the motor ECU  16   a  through the signal line  106 , and the BAT terminal current Ibat is directly inputted to the ECUs  16   a,    26   c  ( FIG. 15 ). 
         [0154]    The FC converter ECU  26   c  is substantially the same as the ECU  26  of the first embodiment. By locking of the wheels, etc., control is implemented to prevent the excessive input of electric power to the battery  30 . Further, by spinning of the wheels, etc., the motor ECU  16   a  control is implemented to prevent excessive output of electric power from the battery  30 . 
       [D2. Control of Fourth Embodiment] 
     (D2-1. Control of FC Converter ECU  26   c ) 
       [0155]    The summary of the control (FC converter control) of the FC converter  24  by the FC converter ECU  26   c  in the fourth embodiment is the same as that of the first embodiment ( FIG. 2 , etc.). The updating cycle Tdir in step S 1  of  FIG. 2  is shorter than the updating cycle Tcan in step S 2 . The same is true in the fourth embodiment. 
       (D2-2. Control of Motor ECU  16   a ) 
     (D2-2-1. Battery Protection Control) 
       [0156]      FIG. 16  is a flowchart showing battery protection control by the motor ECU  16   a  according to the fourth embodiment. In the battery protection control, the motor ECU  16   a  changes the output of the motor  12  through the inverter  14  to achieve protection of the battery  30 . 
         [0157]    In step S 61  of  FIG. 16 , the motor ECU  16   a  updates various sensor values Mdir 2  directly inputted to the motor ECU  16   a.  The various sensor values Mdir 2  herein include the inverter voltage Vinv from the voltage sensor  60  and the inverter current Iinv from the current sensor  64 . Further, in the fourth embodiment, the current sensor  104  is directly connected to the motor ECU  16   a.  Therefore, the BAT terminal current Ibat is also the sensor value Mdir 2 . The updating cycles Tdir 2  of these sensor values Mdir 2  is, e.g., several msec. The updating cycle Tdir 2  may vary for each of the sensor values Mdir 2 . 
         [0158]    In step S 62 , the motor ECU  16   a  updates various control value Ccan 2  and the sensor value Mcan 2  inputted through the CAN  70 . For example, the control values Ccan 2  herein includes the requirement torque Tmreq of the motor  12  from the MG ECU  50 . Additionally, the control values Ccan 2  include the BAT terminal output limit value Pbatlimout from the BAT ECU  32 . Further, for example, the sensor values Mcan 2  include the BAT terminal voltage Vbat. 
         [0159]    The updating cycle Tcan 2  of these control values Ccan 2  and the sensor values Mcan 2  is, e.g., several tens of msec. The updating cycle Tcan 2  is longer than the updating cycle Tdir 2 . The updating cycle Tdir 2  may vary for each of the control values Ccan 2  or the sensor values Mcan 2 . The computation cycle (hereinafter referred to as the “control cycle Tc”) of the steps S 61  to S 66  in  FIG. 16  in the fourth embodiment is, e.g., several msec. The control cycle Tc 2  is equal to the updating cycle Tdir 2  of the sensor values Mdir 2 . For example, it may be possible to use the control cycle Tc 2  which is shorter than the updating cycle Tdir 2  or longer than the updating cycle Tdir 2 , from the viewpoint of making the updating cycle Tdir 2  and the control cycle Tc 2  shorter than the updating cycle Tcan 2 . In step S 63 , the motor ECU  16   a  multiplies the BAT terminal voltage Vbat by the BAT terminal current Ibat to calculate the BAT terminal electric power Pbat. As described above, in the fourth embodiment, the BAT terminal voltage Vbat from the voltage sensor  100  is inputted to the ECU  16   a  through the CAN  70 , and the BAT terminal current Ibat from the current sensor  104  is directly inputted to the ECU  16   a  ( FIG. 15 ). Thus, the BAT terminal voltage Vbat is the sensor value Mcan 2  obtained by the ECU  16   a  through the CAN  70 , and the BAT terminal current Ibat is the sensor value Mdir 2  directly obtained by the ECU  16   a  from the current sensor  104 . Accordingly, the BAT terminal voltage Vbat is updated at the updating cycle Tcan 2 , and the BAT terminal current Ibat is updated at the updating cycle Tdir 2  (&lt;Tcan 2 ). 
         [0160]    In step S 64 , the motor ECU  16   a  determines whether or not the BAT terminal electric power Pbat (S 63 ) is the BAT terminal output limit value Pbatlimout or more. If the BAT terminal electric power Pbat is the limit value Pbatlimout or more (S 64 : YES), in step S 65 , the ECU  16   a  limits the output of the motor  12  from the viewpoint of protecting the battery  30 . For example, the ECU  16   a  decreases the requirement torque Tmreq of the motor  12  by a predetermined amount. In the meanwhile, if the BAT terminal electric power Pbat is not the limit value Pbatlimout or more (S 64 : NO), in step S 66 , the ECU  16   a  does not limit the output of the motor  12  from the viewpoint of protecting the battery  30 . For example, the ECU  16   a  uses the requirement torque Tmreq as it is without any change from the viewpoint of protecting the battery  30  (The ECU  16   a  may limit the output of the motor  12  from other viewpoints.). 
       [D3. Advantages of Fourth Embodiment] 
       [0161]    In the fourth embodiment as described above, the following advantages are obtained in addition to, or instead of the advantages of the first to third embodiments. 
         [0162]    In the fourth embodiment, the motor ECU  16   a  (motor control unit) controls the drive motor  12  using the requirement torque Tmreq (output command values) of the drive motor  12  obtained from the MG ECU  50  (electrical power management unit) through the CAN  70  (first signal system) and the BAT terminal current Ibat (parameter) obtained from the current sensor  104  (parameter acquisition unit) through the signal line  106  (second signal system) ( FIG. 16 ). Therefore, for example, in the normal state, the requirement torque Tmreq is used mainly, and if an instantaneous change occurs in the BAT terminal current Ibat, etc. regarding inputs to, or outputs from the battery  30  (energy storage device) (e.g., rapid increase in the output electric power from the battery  30  resulting from rapid increase in the power consumption of the drive motor  12  due to skidding of the wheels, etc.), by focusing on the change of the BAT terminal current Ibat, etc., it becomes possible to control power generation of the FC  20  (power generation device). Therefore, it becomes possible to protect the battery  30  responsive to the rapid change in the input to, or output from the battery  30 . 
       E. Modified Example 
       [0163]    It is a matter of course that the present invention is not limited to the above described embodiments, and various structures can be adopted based on the description of this specification. For example, the following structure can be adopted. 
       [E1. Applications Where the Invention Is Used] 
       [0164]    In the embodiments, the present invention is applied to the vehicles  10 ,  10 A to  10 C as electric power systems. 
         [0165]    However, for example, from the viewpoint of utilizing a signal path (second signal system) different from the communications network such as the CAN  70  (first signal system), the present invention is not limited in this respect. For example, the present invention may be applied to an electric power system of other types. For example, the present invention may be applied to electric power systems for moving objects such as ships or airplanes. Alternatively, the present invention may be applied to electric power systems for robots, production apparatuses, home use electric power systems, or electric power systems for home appliances. 
       [E2. Structure of Vehicles  10 ,  10 A to  10 C] 
     (E2-1. FC  20  (Power Generation Device)) 
       [0166]    In the above embodiments, the FC 20  (and the motor  12  for regeneration) are used as the power generation device capable of supplying electric power to the battery  30  ( FIG. 1 , etc.). However, for example, from the viewpoint of the power generation device capable of supplying electric power to the battery  30 , the present invention is not limited in this respect. For example, instead of the FC  20 , or in addition to the FC  20 , a generator driven by an engine or other energy storage devices (another battery, capacitor, etc.) which is different from the battery  30  may be used. 
       (E2-2. Drive Motor  12 ) 
       [0167]    In the above embodiments, though the alternating current motor  12  is adopted, from the viewpoint of utilizing a signal path (second signal system) which is different from the communications network (first signal system) such as the CAN  70 , etc., the present invention is not limited in this respect. For example, the motor  12  may be a direct current motor. In this case, an ON/OFF switch may be used instead of the inverter  14 . 
         [0168]    In the above embodiment, the motor  12  is used as a traction motor or a drive motor for the FC vehicles  10 ,  10 A to  10 C. However, for example, from the viewpoint of utilizing a signal path (second signal system) which is different from the communications network (first signal system) such as the CAN  70 , etc., the present invention is not limited in this respect. For example, the motor  12  may be used for in-vehicle devices (such as an electric power steering device, an air compressor, the air conditioner  40 ). 
       (E2-3. FC Converter  24  and BAT Converter  34 ) 
       [0169]    In the above embodiments, the FC  20  and the battery  30  are provided in parallel, the FC converter  24  as the step-up converter is provided in front of the FC  20 , and the BAT converter  34  as the step-up/step-down converter is provided in front of the battery  30  ( FIG. 1 , etc.). However, for example, from the viewpoint of utilizing a signal path (second signal system) which is different from the communications network (first signal system) such as the CAN  70 , the present invention is not limited in this respect. For example, the FC converter  24  provided in front of the FC  20  may be a step-up/step-down converter or a step-down converter, instead of the step-up converter. Alternatively, as shown in  FIG. 17 , the FC  20  and the battery  30  may be provided in parallel, and the FC converter  24  as a step-up, or step-down, or step-up/step-down DC/DC converter may be provided in front of the FC  20 . 
       (E2-4. Current Sensors  104 ,  134 ,  138 , etc. (Parameter Acquisition Unit)) 
       [0170]    In the first and fourth embodiments ( FIGS. 1 and 15 ), the current sensor  104  is connected to the FC converters ECU  26 ,  26   c  through the signal line  106 , and the BAT terminal current Ibat is directly inputted to the FC converter ECU  26 ,  26   c.  In the second embodiment ( FIG. 7 ), the current sensor  134  is connected to the FC converter ECU  26   a  through the signal line  136 , and the primary current Ibatcon 1  of the BAT converter  34  is directly inputted to the ECU  26   a.  In the third embodiment ( FIG. 12 ), the current sensor  138  is connected to the FC converter ECU  26   b  through the signal line  140 , and the secondary current Ibatcon 1  of the BAT converter  34  is directly inputted to the ECU  26   b.    
         [0171]    However, for example, from the viewpoint of directly inputting parameters regarding the input to, or output from the battery  30  (energy storage device) to the FC converter ECUs  26 ,  26   a  to  26   c,  the present invention is not limited in this respect. For example, in the cases of first and fourth embodiments, in addition to the BAT terminal current Ibat, or instead of the BAT terminal current Ibat, the BAT terminal voltage Vbat may be directly inputted to the FC converter ECUs  26 ,  26   c.  In the second embodiment, in addition to, or instead of the primary current Ibatcon 1 , the primary voltage Vbatcon 1  is directly inputted to the FC converter ECU  26   a.    
         [0172]    In the fourth embodiment, the current sensor  104  is connected to the motor ECU  16   a  through the signal line  106 , and the BAT terminal current Ibat is directly inputted to the ECU  16   a  ( FIG. 15 ). However, for example, from the viewpoint of directly inputting parameters regarding the input to or the output from the battery  30  (energy storage device), to the motor ECU  16   a,  the present invention is not limited in this respect. For example, instead of, or in addition to the BAT terminal current Ibat, the BAT terminal voltage Vbat may be directly inputted to the motor ECU  16   a.  Further, for example, from the viewpoint of using the estimated BAT terminal electric power Pbatest, Pbatest 2  (S 43  of  FIG. 9 , S 53  of  FIG. 14 ) in the motor ECU  16   a,  the primary current Ibatcon 1  of the BAT converter  34  detected by the current sensor  134  or the secondary current Ibatcon 2  of the BAT converter  34  detected by the current sensor  138  may be directly inputted to the ECU  16   a  (see the second and third embodiments). 
       (E2-5. CAN  70  and Signal Lines  106 ,  136 ,  140  (First Signal System and Second Signal System) 
       [0173]    In the first and fourth embodiments, the sensor values Mdir, Mdir 2 , Mcan, Mcan 2 , and control values Ccan, Ccan 2  are inputted to the FC converter ECU  26 ,  26   c,  and the motor ECU  16   a  using the CAN  70  and the signal line  106  ( FIGS. 1 and 15 ). However, for example, from the viewpoint of using the second signal system having the shorter arrival time to the destination point (FC converter ECUs  26 ,  26   a  to  26   c ) in comparison with the first signal system for transmitting the sensor values Mcan, Mcan 2 , and the control values Ccan, Ccan 2 , the present invention is not limited in this respect. For example, a low speed CAN may be used for the first signal system for transmitting the sensor values Mcan, Mcan 2  and the control values Ccan, Ccan 2 , and a high speed CAN may be used for the second signal system for transmitting the sensor values Mdir, Mdir 2 . Alternatively, LIN (Local Interconnect Network), FlexRay, etc. may be used for the first signal system or the second signal system. 
       (E2-6. FC Converter ECUs  26 ,  26   a  to  26   c ) 
       [0174]    In the FC converter ECUs  26 ,  26   a  to  26   c  of the above embodiments, in order to avoid overcharging of the battery  30 , in the case where the input electric power to the battery  30  becomes large, the primary current Ifccon 1  of the FC converter  24  is decreased (see  FIG. 6 , etc.). However, for example, from the viewpoint of protecting the battery  30 , the present invention is not limited in this respect. For example, in the FC converter ECUs  26 , and  26   a  to  26   c,  in order to avoid overdischarging by the battery  30 , in the case where the output electric power from the battery  30  is large (in the case where the output electric power or parameters related to the output electric power exceeds a predetermined threshold value), it is possible to increase the primary current Ifccon 1  of the FC converter  24 . 
         [0175]    In the first embodiment, the FC converter ECU  26  corrects the requirement primary current Ifccon 1 req (power generation command value of the FC  20  (power generation device)) obtained from the MG ECU  50  through the CAN  70  (first signal system) using the BAT terminal current Ibat (parameter) ( FIG. 1 ) obtained from the current sensor  104  (parameter acquisition unit) through the signal line  106  (second signal system) to control the FC  20  (power generation device) ( FIGS. 3 and 6 , etc.). 
         [0176]    However, for example, from the viewpoint of using the requirement primary current Ifccon 1 req (power generation command value of the FC  20  (power generation device)) obtained through the CAN  70  (first signal system) and the BAT terminal current Ibat (parameter) obtained from the current sensor  104  (parameter acquisition unit) through the signal line  106  (second signal system), the present invention is not limited in this respect. For example, in the case where a rapid change (change exceeding a threshold value) has occurred in the BAT terminal current Ibat, it is possible to control the FC  20  based on the BAT terminal electric current Ibat without using the requirement primary current Ifccon 1 req. The same holds for the FC converter ECUs  26   a  to  26   c  according to the second to fourth embodiments. 
         [0177]    In the above embodiments, the FC converter ECUs  26 ,  26   a  to  26   c  use the requirement primary current Ifccon 1 req obtained from the MG ECU  50  through the CAN  70  (first signal system) as the power generation command value of the FC  20  (power generation device ( FIG. 1 , etc.). However, for example, from the viewpoint of controlling power generation of the FC  20  (power generation device), the present invention is not limited in this respect. The requirement values of the secondary current Ifccon 2  of the FC converter ECUs  26 ,  26   a  to  26   c  may be used as power generation command values of the FC  20 . 
         [0178]    In the above embodiments, the primary current limit value Ifccon 1 lim 2  of the FC converter  24  (input electric power threshold value of the battery  30  (energy storage device) is determined based on the temperature Tbat and the SOC of the battery  30  (S 12  of  FIG. 4 ). However, from the viewpoint of setting the primary current limit value Ifccon 1 lim 2 , it is also possible to set the primary current limit value Ifccon 1 lim 2  only using one of the temperature 
         [0179]    Tbat and SOC of the battery  30 . Further, for example, from the viewpoint of determining the primary current limit value Ifccon 1 lim 1 , it is also possible not to set the primary current limit value Ifccon 1 lim 2 . 
       (E2-7. Motor ECU  16   a ) 
       [0180]    In the motor ECU  16   a  of the fourth embodiment, in order to avoid overdischarging of the battery  30 , in the case where the output electrical power from the battery  30  is large, the output of the motor  12  is limited (see  FIG. 16 ). However, for example, from the viewpoint of protecting the battery  30 , the present invention is not limited in this respect. For example, in the motor ECU  16   a,  in order to avoid overcharging of the battery  30 , in the case where the input electric power to the battery  30  is large (in the case where the input electric power or the associated parameter exceeds a predetermined threshold value), it is also possible to temporarily increase the output of the motor  12 . 
         [0181]    In the fourth embodiment, the motor ECU  16   a  corrects the requirement torque Tmreq (output command values of the motor  12 ) obtained from the MG ECU  50  through the CAN  70  (first signal system) using the BAT terminal current Ibat (parameter) obtained from the current sensor  104  (parameter acquisition unit) through the signal line  106  (second signal system) ( FIG. 15 ) to control the motor  12  ( FIG. 16 ). However, for example, from the viewpoint of using the requirement torque Tmreq (output command value of the motor  12 ) obtained through the CAN  70  (first signal system) and the BAT terminal current Ibat (parameter) obtained from the current sensor  104  (parameter acquisition unit) through the signal line  106  (second signal system), the present invention is not limited in this respect. For example, in the case where a rapid change (change above a threshold value) has occurred in the BAT terminal current Ibat, it is also possible to control the motor  12  based on the BAT terminal current Ibat without using the requirement torque Tmreq.