Abstract:
Provided is a vehicle charging device ( 170 ) that uses a power source ( 101 ) outside of a vehicle ( 160 ) to charge a battery ( 115 ) installed in the vehicle ( 160 ). A charger ( 114 ) charges the battery ( 115 ). A voltage measurement unit ( 111 ) measures the input voltage corresponding to the input current in the charger ( 114 ). A current measurement unit ( 112 ) measures the input current (Ic) in the charger ( 114 ). A control unit ( 113 ) changes the input currents (Ic) of the charger ( 114 ) into a plurality of values, and controls the input current (Ic) when the input voltage (Vc) has changed, according to the corresponding relationship between the input currents (Ic), when each has been changed, and the measured input voltages (Vc).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an in-vehicle charging apparatus configured to charge a storage battery serving as the power source of a vehicle such as an electric vehicle, using a power supply of a house, for example. 
       BACKGROUND ART 
       [0002]    In recent years, charging of storage batteries installed in a vehicle such as an electric vehicle using a power supply of a house (house of the owner of the vehicle) has been in practice. Since the power supply of a house supplies power to various electric devices such as an air conditioner, an overcurrent flowing through a power supply circuit may be caused by, for example, an increase in the number of electric devices in use. When an overcurrent occurs, the power supply circuit is shut off to stop supply of the power to the electric devices, thus making all the electric devices temporarily unusable. 
         [0003]    Conventionally, electric device systems configured to reduce a current amount according to a decrease in a receiving voltage have been known as a method of preventing an overcurrent flowing through a power supply circuit in a house (for example, Patent Literature (hereinafter, abbreviated as PTL) 1). In an electric device system of PTL 1, when a decrease in a receiving voltage is detected by a voltage detector, a current amount in the entire system is reduced by controlling a power converter according to this decrease. 
       CITATION LIST 
     Patent Literature 
     PTL 1 
       [0000]    
       
         Japanese Patent Application Laid-Open No. 2003-92829 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0005]    The system according to PTL 1, however, reduces a current amount of the system without taking into consideration a current amount for other electric devices in use. As a result, the occurrence of overcurrent due to a current used in the entire system involves a problem in that all the electric devices become temporarily unusable because the power supply circuit is shut off. 
         [0006]    It is an object of the present invention to provide an in-vehicle charging apparatus capable of preventing an in-vehicle charger from becoming unable to perform charge and also preventing an unusable state of another electric device in a house or the like by decreasing the input current of the in-vehicle charger when the use of the other electric device is started during the charge in the house or the like. 
       Solution to Problem 
       [0007]    An in-vehicle charging apparatus according to an aspect of the present invention is an apparatus installed in a vehicle and configured to charge a storage battery installed in the vehicle, using a power source that is connected to an electric device and that is provided outside the vehicle, the apparatus including: a charger that receives a variable input current value flowing from the power source for charging the storage battery; a measurement section that measures the input current value of the charger and an input voltage value on the side of the power source of the charger; and a control section that controls the input current value of the charger, in which: the control section varies the input current value of the charger into a plurality of values, and calculates a correspondence between the input current values measured by the measurement section during the varying, and input voltage values corresponding to the respective input current values; and the control section controls, when an input voltage value varies while the input current value measured by the measurement section remains the same during charge of the storage battery, the input current value of the charger so that the input current value of the charger corresponds to the input voltage value before the varying, based on the correspondence. 
       Advantageous Effects of Invention 
       [0008]    According to the present invention, it is possible to prevent an in-vehicle charger from becoming unable to perform charge and also to prevent an unusable state of another electric device in a house or the like by decreasing the input current of the in-vehicle charger when the use of the other electric device is started during the charge in the house or the like. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]      FIG. 1  illustrates a configuration of a charging system according to an embodiment of the present invention; 
           [0010]      FIG. 2  illustrates the relationship between time and an input current in a method of finding the relationship between an input voltage and an input current as a first-order approximation straight line according to the embodiment of the present invention; 
           [0011]      FIG. 3  is a flowchart illustrating how to find a first-order approximation straight line according to the embodiment of the present invention; 
           [0012]      FIG. 4  illustrates the relationship between an input voltage and an input current on the found first-order approximation straight line according to the embodiment of the present invention; 
           [0013]      FIG. 5  is a flowchart illustrating a control method of the input current of a charger after the start of charge according to the embodiment of the present invention; 
           [0014]      FIG. 6  illustrates a control for decreasing the input current of the charger after the start of charge according to the embodiment of the present invention; and 
           [0015]      FIG. 7  illustrates a control for increasing the input current of the charger after the start of charge according to the embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0016]    Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
       Embodiments 
     &lt;Configuration of Charging System&gt; 
       [0017]      FIG. 1  illustrates a configuration of charging system  100  according to an embodiment of the present invention. 
         [0018]    House  150  is a house of the owner of vehicle  160 , for example. House  150  includes socket  105  connected to in-vehicle charging apparatus  170  of vehicle  160 . House  150  has power supply circuit  180  that supplies a power supply current from power source  101 . House  150  includes breaker board  106  that shuts off power supply circuit  180  when an overcurrent flows through power supply circuit  180 . 
         [0019]    Vehicle  160  charges storage battery  115  installed in vehicle  160 , by in-vehicle charging apparatus  170  connected to socket  105 , using power source  101  supplied to the inside of house  150  from, for example, a power plant. Vehicle  160  is an electric vehicle which runs using storage battery  115  as a driving source. 
         [0020]    In-vehicle charging apparatus  170  charges storage battery  115  installed in vehicle  160 . A configuration of in-vehicle charging apparatus  170  will be described below in detail. 
         [0021]    Power supply circuit  180  includes power source  101 , output impedance  102  of power source  101 , and impedance  104  of the wiring which connects power source  101  and charger  114 . Power supply circuit  180  is a circuit for supplying a power source from power source  101  to electric device  103  or in-vehicle charging apparatus  170 . 
         [0022]    &lt;Configuration of in-Vehicle Charging Apparatus&gt; 
         [0023]    In-vehicle charging apparatus  170  has voltage measurement section  111 , current measurement section  112 , control section  113 , and charger  114 . 
         [0024]    Voltage measurement section  111  measures the input voltage of charger  114  and outputs the measured voltage value to control section  113 . 
         [0025]    Current measurement section  112  measures the input current of charger  114  corresponding to the input voltage of charger  114  and outputs the measured current value to control section  113 . 
         [0026]    Control section  113  finds for the relationship between the plurality of measured voltage values inputted from voltage measurement section  111  and the plurality of measured current values corresponding to the plurality of respective measured voltage values inputted from current measurement section  112  as a first-order approximation straight line, and stores the found values as a table. Control section  113  controls the input current of charger  114  according to the table of the found first-order approximation straight line. A method of finding a first-order approximation straight line and a control method of the input current during the charge will be described below. 
         [0027]    Charger  114  charges storage battery  115  with an input current controlled by control section  113 , using power source  101 . 
         [0028]    &lt;Method of Finding First-Order Approximation Straight Line&gt; 
         [0029]      FIG. 2  illustrates the relationship between time and an input current in a method of finding the relationship between an input voltage and an input current as a first-order approximation straight line.  FIG. 3  is a flowchart illustrating how to find a first-order approximation straight line in the present embodiment.  FIG. 4  illustrates the relationship between an input voltage and an input current on the found first-order approximation straight line. 
         [0030]    Control section  113  finds a first-order approximation straight line, for example, before the start of charge. 
         [0031]    Control section  113  varies input current Ic in sequence at predetermined time intervals and acquires the measured value of input voltage Vc at every timing of varying input current Ic. For example, as illustrated in  FIG. 2 , control section  113  varies input current Ic in sequence in order of “0,” “1/4 Icmax,” “2/4 Icmax,” “3/4 Icmax,” and “Icmax,” and acquires the measured value of each input voltage Vc. Input current Ic and input voltage Vc which have been acquired are associated and stored in a table. 
         [0032]    Specifically, as illustrated in  FIG. 3 , voltage measurement section  111  first measures input voltage Vc corresponding to input current Ic=0 (Step ST 301 ). 
         [0033]    Next, voltage measurement section  111  measures input voltage Vc corresponding to input current Ic=1/4 Icmax (Step ST 302 ). 
         [0034]    Next, voltage measurement section  111  measures input voltage Vc corresponding to input current Ic=2/4 Icmax (Step ST 303 ). 
         [0035]    Next, voltage measurement section  111  measures input voltage Vc corresponding to input current Ic=3/4 Icmax (Step ST 304 ). 
         [0036]    Next, voltage measurement section  111  measures input voltage Vc corresponding to input current Ic=Icmax (Step ST 305 ). 
         [0037]    Next, control section  113  acquires input current Ic and input voltage Vc in each of Steps ST 301  to ST 304 , and finds the relationship between input current Ic and input voltage Vc which are acquired as a first-order approximation straight line using the least-squares method (Step ST 306 ). 
         [0038]    Next, control section  113  determines whether the error of the least-squares method used for finding the first-order approximation straight line is equal to or less than a constant value (Step ST 307 ). 
         [0039]    When the error of the least-squares method is equal to or less than the threshold (Step ST 307 : YES), and control section  113  determines the first-order approximation straight line found in Step ST 306  (Step ST 308 ), and complete the process. 
         [0040]    On the other hand, when the error of the least-squares method is larger than a threshold value, (Step ST 307 : NO) control section  113  repeats the process of Steps ST 301  to ST 306 . 
         [0041]    With the above-described method, control section  113  finds the relationship between the value of each varied input current Ic and the measured value of each input voltage Vc corresponding to each input current Ic, as first-order approximation straight line # 301  illustrated in  FIG. 4 . The method of finding first-order approximation straight line # 301  is not limited to the least-squares method, and any other appropriate methods can be used. 
         [0042]    The slope of first-order approximation straight line # 301  is equal to synthetic impedance Zs (Zs=ZP+ZL) obtained by synthesizing output impedance ZP of power source  101  and impedance ZL of the wiring between power source  101  and charger  114 . 
         [0043]    &lt;Control Method of Input Current of Charger During Charge&gt; 
         [0044]    When the amount of power used for electric device  103  in house  150  increases during the charge of in-vehicle charging apparatus  170 , the input voltage to charger  114  declines as a result. In this case, the control is performed as follows. 
         [0045]      FIG. 5  is a flowchart illustrating a control method of the input current of charger  114  after the start of charge.  FIG. 6  illustrates a control for decreasing the input current of charger  114  after the start of charge.  FIG. 7  illustrates a control for increasing the input current of charger  114  after the start of charge. 
         [0046]    In  FIG. 6 , Vc 1  is the input voltage before the decrease, Vc 2  is the input voltage after the decrease, Ic 1  is the input current before the decrease, and Ic 2  is the input current after the decrease. ΔVcr is a voltage reduction caused by an increase in load current Id flowing through electric device  103 . ΔIcr is a current decreased by the control of control section  113 . Vkr is the value of input voltage Vc at the intersection of first-order approximation straight line # 301  and the vertical axis. 
         [0047]    In  FIG. 7 , Vc 3  is the input voltage before the increase, Vc 4  is the input voltage after the increase, Ic 3  is the input current before the increase, and Ic 4  is the input current after the increase. ΔVcs is a voltage rise caused by a decrease in load current Id flowing through electric device  103 . ΔIcs is a current increased by the control of control section  113 . Vks is the value of input voltage Vc at the intersection of first-order approximation straight line # 301  and the vertical axis. 
         [0048]    Control section  113  controls the input current of charger  114  using first-order approximation straight line # 301  beforehand found after the start of charge. 
         [0049]    First, control section  113  acquires the measured value of input voltage Vc from voltage measurement section  111  and also acquires the measured value of input current Ic from current measurement section  112  (Step ST 501 ). 
         [0050]    Next, control section  113  determines whether the charge is necessary (Step ST 502 ). For example, control section  113  determines that the charge is unnecessary when storage battery  115  is fully charged, and determines that the charge is necessary when storage battery  115  is not fully charged. 
         [0051]    When determining that the charge is unnecessary (Step ST 502 : NO), control section  113  completes the process. 
         [0052]    On the other hand, when determining that the charge is necessary (Step ST 502 : YES), control section  113  determines whether the acquired measured value of the input voltage and the acquired measured value of the input current are positioned on first-order approximation straight line # 301  (Step ST 503 ). 
         [0053]    When the input voltage is stable and the values are positioned on first-order approximation straight line # 301  (Step ST 503 : YES), an overcurrent does not flow through power supply circuit  180  even if the input current of charger  114  is not adjusted. Control section  113  therefore returns to the process of Step ST 502 . 
         [0054]    On the other hand, when the values are not positioned on first-order approximation straight line # 301  (Step ST 503 : NO), control section  113  determines whether input voltage Vc decreases (Step ST 504 ). 
         [0055]    When input voltage Vc decreases (Step ST 504 : YES), control section  113  controls charger  114  so as to decrease input current Ic according to first-order approximation straight line # 301  (Step ST 505 ). 
         [0056]    Specifically, as illustrated in  FIG. 6 , assuming that input current Ic is constant when input voltage Vc decreases from Vc 1  to Vc 2 , control straight line # 601  is found which has the same slope as that of first-order approximation straight line # 301  and passes through input voltage Vc 2  after the decrease. Control section  113  controls charger  114  so as to decrease input current from Ic 1  so that the input voltage on found control straight line # 601  is substantially equal to input voltage Vc 1  before the decrease. Here, input voltage Vc substantially equal to input voltage Vc 1  is equal to or more than input voltage Vc 1  and equal to or less than a value larger than input voltage Vc by predetermined value α (where α&gt;0) (Vc 1 ≦Vc≦(Vc 1 +α)). This is a concept including a control for decreasing input current from Ic 1  to an input current corresponding to a voltage higher than input voltage Vc 1  before the decrease by predetermined value α. 
         [0057]    On the other hand, when input voltage Vc does not decrease (Step ST 504 : NO), control section  113  controls charger  114  so as to increase input current Ic (Step ST 506 ). 
         [0058]    Specifically, as illustrated in  FIG. 7 , assuming that input current Ic is constant when input voltage Vc increases from Vc 3  to Vc 4 , control straight line # 701  is found which has the same slope as that of first-order approximation straight line # 301  and passes through input voltage Vc 4  after the increase. Control section  113  controls charger  114  so as to increase the input current from Ic 4  so that the input voltage on found control straight line # 701  is substantially equal to input voltage Vc 3  before the increase. However, at this time, control section  113  controls the input current so as not to be equal to or more than maximum allowable current value Icmax. Here, input voltage Vc substantially equal to input voltage Vc 3  is equal to or less than input voltage Vc 3  and equal to or more than a value smaller than input voltage Vc by predetermined value β (where β&gt;0) (Vc 3 ≧Vc≧(Vc 3 −β)). This is a concept including a control for increasing the input current from Ic 4  to an input current corresponding to a voltage lower than input voltage Vc 3  before the increase by predetermined value β. 
         [0059]    Alternatively, in  FIG. 5 , the process in Step ST 502 , which is to determine whether the charge is necessary may be performed, and after it is determined that the charge is necessary, the process in Step ST 501 , which is to acquire the measured value of input voltage Vc from voltage measurement section  111  and the measured value of input current Ic from current measurement section  112 , may be performed. 
         [0060]    &lt;Specific Example of Controlling to Decrease Input Current Ic 1  to Input Current Ic 2 &gt; 
         [0061]    With reference to  FIG. 5 , an example case will be described in which in-vehicle charging apparatus  170  starts the charge for storage battery  115  using power source  101  when electric device  103  is stopped, and then electric device  103  starts to operate by receiving power supplied from power source  101 . 
         [0062]    Voltage reduction ΔVc caused by the start of operation of electric device  103  can be found by Equation 1. 
         [0000]      [1] 
         [0000]      Δ Vc−ZP*ΔId   (Equation 1)
 
         [0063]    where Id is a current flowing through electric device  103 , and 
         [0064]    ZP is the output impedance of power source  101 . 
         [0065]    Control section  113  decreases input current Ic to compensate the influence of voltage reduction ΔVc found from Equation 1. 
         [0066]    Here, input voltage Ve can be found by Equation 2. 
         [0000]      [2] 
         [0000]        Vc=Vp−ZP ( Ic+Id )− ZL*Ic   (Equation 2)
 
         [0067]    where Vp is the voltage of power source  101 , 
         [0068]    Ic is a current flowing from point A (refer to  FIG. 1 ) of breaker board  106  to charger  114 , 
         [0069]    Id is a current flowing through electric device  103 , 
         [0070]    ZP is the output impedance of power source  101 , and 
         [0071]    ZL is the impedance of wiring between power source  101  and charger  114 . 
         [0072]    Equation 2 is modified to give input voltage Vc by Equation 3. 
         [0000]      [3] 
         [0000]        Vc =( Vp−ZP*Id )− ZS*Ic   (Equation 3)
 
         [0073]    where Zs is the synthetic impedance of ZP and ZL. 
         [0074]    Output voltage Vk of breaker board  106  for input current Ic=0 can be found by Equation 4. 
         [0000]      [4] 
         [0000]        Vk=Vp−ZP*Id   (Equation 4)
 
         [0075]    where Vp is the voltage of power source  101 , 
         [0076]    Id is a current flowing through electric device  103 , and 
         [0077]    ZP is the output impedance of power source  101 . 
         [0078]    Equation 4 is substituted for Equation 3 to obtain Equation 5. 
         [0000]      [5] 
         [0000]        Vc=Vk−Zs*Ic   (Equation 5)
 
         [0079]    From Equation 5, input voltage Vc 1  before the decrease and input voltage Vc 2  after the decrease are obtained by Equations 6 and 7, respectively. 
         [0000]      [6] 
         [0000]        Vc 1 =Vk−ZS*Ic 1  (Equation 6)
 
         [0000]      [7] 
         [0000]        Vc 2 =Vk−ZS*Ic 2  (Equation 7)
 
         [0080]    Since voltage reduction ΔVc=Vc 2 −Vc 1 , Equation 6 is subtracted from Equation 7 to thereby obtain voltage reduction ΔVc by Equation 8. 
         [0000]      Δ Vc=−ZS*ΔIc   (Equation 8)
 
         [0081]    Equation 8 can be modified to obtain Equation 9. 
         [0000]      [9] 
         [0000]      Δ Ic=−ΔVc/ZS   (Equation 9)
 
         [0082]    Therefore, decrease amount ΔIc of input current Ic compensating the influence of voltage reduction ΔVc can be found by Equation 9. 
         [0083]    Here, Equation 1 is substituted for Equation 9 to obtain Equation 10. 
         [0000]      [10] 
         [0000]      Δ Id =−( ZS/ZP )*Δ Ic   (Equation 10)
 
         [0084]    From Equation 10, since (ZS/ZP)≧1, ΔIc≦ΔId. Therefore, a decrease amount of ΔIc can be increased according to an increase in ΔId, and an increase amount of ΔIc can be increased according to a decrease in ΔId. 
       Advantageous Effects of Present Embodiment 
       [0085]    As described above, in the present embodiment, the relationship between the input voltage and the input current of the charger is found as a first-order approximation straight line before the start of charge, and thereby, the input current of the charger is controlled according to the first-order approximation straight line after the start of charge. Thereby, according to the present embodiment, it is possible to prevent an in-vehicle charger from becoming unable to perform charge and also to prevent an unusable state of another electric device by decreasing the input current of the in-vehicle charger after the use of the other electric device is started during the charge. 
         [0086]    According to the present embodiment, an input current is reduced according to a decrease in an input voltage caused by the start of the use of another electric device during the charge, and an input current is increased according to an increase in an input voltage caused by the stop of the use of the other electric device during the charge. As a result, charging with a maximum input current usable for charge can be used for the charge. 
         [0087]    According to the present embodiment, a first-order approximation straight line is found again when a large error is caused from the least-squares method used for finding a first-order approximation straight line. Thereby, according to the present embodiment, it is possible to avoid finding an inaccurate first-order approximation straight line due to a variation in an input voltage caused by the start or stop of operation of another electric device while a first-order approximation straight line is found. 
       Variations of Present Embodiment 
       [0088]    In the above-described embodiment, a control that decreases or increases the input current of charger  114  by a single level is performed. However, the present invention is not limited to this configuration, and a control that decreases or increases the input current of charger  114  by a plurality of levels may be performed. 
         [0089]    In the above-described embodiment, a first-order approximation straight line is found before the start of charge, and the input current of the charger is controlled according to the first-order approximation straight line after the start of the charge. However, the present invention is not limited to this configuration, and a first-order approximation straight line may be found at predetermined timing after the start of charge. 
         [0090]    The disclosure of Japanese Patent Application No. 2011-75791, filed on Mar. 30, 2011, including the specification, drawings and abstract, is incorporated herein by reference in its entirety. 
       INDUSTRIAL APPLICABILITY 
       [0091]    An in-vehicle charging apparatus according to the present invention is suitable for charging a storage battery serving as the power source of a vehicle such as an electric vehicle, using the power supply of a house, for example. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           100  Charging system 
           101  Power source 
           102  Output impedance 
           103  Electric device 
           104  Impedance 
           105  Socket 
           106  Breaker board 
           111  Voltage measurement section 
           112  Current measurement section 
           113  Control section 
           114  Charger 
           115  Storage battery 
           150  House 
           160  Vehicle 
           170  In-vehicle charging apparatus 
           180  Power supply circuit