Abstract:
Provided is a battery system including battery modules each having a plurality of batteries and a battery module control unit for controlling the plurality of batteries, and battery pack control units for controlling a plurality of the battery module control units, wherein the plurality of the battery module control units are connected in serial by wires between modules, wherein each battery module control unit includes a first input/output terminal for inputting or outputting information to or from a battery module control unit of one adjacent battery module and a second input/output terminal for inputting or outputting information to or from a battery module control unit of another adjacent battery module, and wherein an input impedance of the first input/output terminal is smaller than an input impedance of the second input/output terminal.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a battery system having a control controller installed therein. 
         [0003]    2. Description of the Related Art 
         [0004]    Battery systems, the development of which has been progressing in recent years, can be applied in many ways, and the size of each battery system varies in accordance with the purpose of usage. Especially, battery systems which are used for load variation control and power outage solutions of a server center, stabilizing a large scale system such as a regenerative power absorption system of a railroad, a renewable energy system, and a nuclear power plant, are large. 
         [0005]    In the case where the battery system has a plurality of battery modules, in order to communicate with or control the plurality of battery modules, it has been considered to perform one on one communication between an upper electrical potential and a lower electrical potential by connecting the battery module control units respectively provided in each of the battery modules in a daisy chain manner, and perform communication by means of a bus connection in the parallel direction. In this case, it is necessary to prepare a battery system in which two termination resistors are provided between each of the battery modules, and a termination resistor is mounted in the beginning part and the termination part of the bus connection. According to such a configuration, the number of parts increases in a large-scale battery system. 
         [0006]    JP-A-10-105305 discloses a battery system including a selector circuit which uses an external connector for selecting whether to mount a termination resistor, thereby reducing the number of the termination resistors. 
       SUMMARY OF INVENTION 
       [0007]    However, in a method of mounting a termination resistor relating to the conventional technology, it is necessary to add a mounting selection circuit, thus it is not possible to solve the problem that the number of parts increases. In addition, setting operation of mounting selection accompanies addition of the mounting selection circuit, thus communication delays and the like occur. 
         [0008]    Consequently, considering the above problem, the object of the present invention is to provide a battery system in which communication delays do not occur while reducing the number of parts of the termination resistor. 
         [0009]    According to an aspect of the invention, there is provided a battery system including a battery module having a plurality of batteries and a battery module control unit for controlling the plurality of batteries, and a battery pack control unit for controlling a plurality of the battery module control units, wherein the plurality of battery module control units are connected in serial by a wire between modules, wherein each battery module control unit includes a first input/output terminal for inputting or outputting information to or from a battery module control unit of an adjacent battery module and a second input/output terminal for inputting or outputting information to or from a battery module control unit of an adjacent battery module, and wherein an input impedance of the first input/output terminal is smaller than an input impedance of the second input/output terminal. 
         [0010]    According to the aspect of the invention, it is possible to provide a battery system capable of restricting communication delays while reducing the number of parts of the termination resistors. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a view illustrating a power generation system according to the present invention. 
           [0012]      FIG. 2  is a block diagram of a battery system according to the present invention. 
           [0013]      FIG. 3  is a circuit diagram of a battery module according to the present invention. 
           [0014]      FIG. 4  is a circuit diagram of a battery pack according to the present invention. 
           [0015]      FIG. 5  is a circuit diagram of a battery system according to the present invention. 
           [0016]      FIG. 6  is an outline diagram of the battery pack according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
       [0017]    Hereinafter, it will be described about an embodiment of the present invention with reference to the accompanying drawings. First, a power generation system  101  relating to the present invention will be described using  FIG. 1 . The power generation system  101  includes a power generating apparatus  103 , a power system  102 , an electric wire  105  to connect the power system  102  with the power generating apparatus  103 , a battery system  201  connected to the electric wire  105  through an inverter  104 . Examples of the power generating apparatus  103  include wind power generation equipment, hydroelectric power generation equipment, and photovoltaic power generation equipment, or other generation equipment. 
         [0018]    If the power generating apparatus  103  generates power in excess of the power requested in the power system  102 , the battery system  201  charges with the excessively generated power, on the contrary, if the power generating apparatus  103  generates less power than the power requested in the power system  102 , the battery system  201  discharges the charged power, thereby aiming to stably supply power. Also, in the case where the battery system  201  performs charging or discharging, reception or supply of power is performed while an AC to DC conversion or a DC to AC conversion is performed by the inverter  104 . 
         [0019]    Subsequently, a block diagram of the battery system  201  is shown in  FIG. 2 . The battery system  201  according to the present invention includes battery blocks  50  having a plurality of battery packs  40 , the battery packs  40  having a plurality of battery modules  30 , using a battery module  30  as a minimum unit. 
         [0020]    The specific explanation of the configuration of the battery module  30  will be given. The battery module  30  includes a plurality of battery cell groups  20 , cell control units (CCU)  210  to collect battery information of the battery cell groups  20  (for example, current information, voltage information, temperature information, charging state, and the like of the battery cell) and a battery module control unit (BMCU)  31 . In addition, the cell control unit  210  performs balancing control between the battery cells described below. The battery information collected in the cell control unit  210  is sent to the battery module control unit (BMCU)  31 . Also, in the battery module control unit (BMCU)  31 , average charging state of the battery cell groups  20  inside the battery module  30  is calculated and battery information of average charging state of the battery cell groups  20  is added to the above battery information to supply an upper battery pack control unit (BPCU)  230  with battery information. 
         [0021]    The battery pack  40  has the plurality of battery modules  30  and a battery pack control unit  230 . The battery pack control unit  230  collects battery information output from each battery module control unit  31  to calculate information about average charging state of the battery module  30  obtained by taking an average of the charging states of the battery modules  30  inside the battery pack  40 . By adding the information about average charging state of the plurality of battery modules  30  to battery information obtained from the battery module control units  31 , the battery information is output to an upper battery block control unit  240 . 
         [0022]    The battery block  50  has a plurality of battery packs  40  and a battery block control unit  240 . The battery block control unit  240  collects battery information output from each battery pack control unit  230  to calculate information about average charging state of the battery pack  40  obtained by taking an average of the charging state of the battery pack  40  inside the battery block  50 . By adding the information about average charging state of the plurality of battery packs  40  to battery information obtained from the battery pack control unit  230 , the battery information is output to an upper system control unit  250 . Though the description states that the battery block  50  has a plurality of battery packs  40 , the number of the battery packs  40  constituting the battery block  50  may be one. In that case, the battery block control unit  240  outputs the battery information as it is output from the battery pack control unit  230  to the system control unit  250 . 
         [0023]    In the present invention, since the state of the battery is monitored in the plurality of layers, the battery system  201  has high safety performance. Since each of the battery module  30 , the battery pack  40  and the battery block  50  according to the present invention can be replaced in each unit, the battery system has good maintainability. 
         [0024]    Subsequently, it will be specifically described about the circuit configuration of the battery module  30  using  FIG. 3 . The battery module  30  includes a power source circuit  25  connected in serial with the plurality of battery cell groups  20  and a fuse  32  connected in serial with the power source circuit provided therein. The battery cell group  20  has a configuration in which a plurality of battery cells Bn 1 , Bn 2  . . . BnX are connected in parallel (where, n is a number greater than 1, indicating the number of battery cell groups  20  connected in serial. X is the number of the cells). Also, a resistor element  21  and a switch element  22  are connected in parallel with the battery cell group  20 . The resistor element  21  and the switch element  22  are for performing balancing between battery cells B 11 , B 12  . . . B 1 X when there is variation in voltages between or charging states of, for example, the battery cells B 11 , B 12  . . . B 1 X. 
         [0025]    The cell control unit  210  obtains battery information of each of the battery cells Bn 1 , Bn 2  BnX to output the obtained information to the battery module control unit  31 . The battery module control unit  31  calculates the state of charging (SOC) of each battery cell based on the battery information output from each cell control unit  210  to output charging state information to the cell control unit  210 . When differences among the charging states of the battery cells Bn 1 , Bn 2  . . . BnX inside the battery cell group  20  that the cell control unit  210  monitors become 10% or more, the cell control unit  210  which receives the charging state information outputs a signal to make the switch element  22  ON state to perform balancing between the battery cells Bn 1 , Bn 2  BnX. 
         [0026]    In addition, in the aforementioned battery module control unit  31 , there are a CAN communication connecting portion  33   a  and  33   b.  The battery module control unit  31  is connected to other battery module control unit  31  through CAN communication connecting portion  33   a  and  33   b,  however, the detailed description thereof will be given using  FIG. 4 . 
         [0027]      FIG. 4  shows a circuit diagram of the battery pack  40 . The battery pack  40  is configured such that a plurality of module serial bodies  300  to which the plurality of battery modules  30  are connected in serial, are connected in parallel, and each of the plurality of module serial bodies  300  connected in parallel is communicated and controlled by one battery pack control unit  230 . 
         [0028]    Subsequently, it will be described about connection between the battery pack control unit  230  and the battery module control unit  31  of each of the battery modules  30  constituting the module serial body  300 . The battery pack control unit  230  and the battery module control units  31  are connected by a connection wire  36 . In addition, a termination resistor  235  is provided in the battery pack control unit  230 . Also, a termination resistor  236  is provided in the end of the connection wire  36 . Though the resistance is determined by a transceiver used in CAN communication in the present invention, the resistance value of the termination resistor  235  may be 60Ω. The resistance value of the termination resistor  236  may also be 60Ω. The resistance values are set to the values, thereby restricting noise due to signal reflection in the case of performing CAN communication. On the other hand, in the case where a pattern which makes impedance asymmetric is considered, the termination resistor may be configured such that the resistance value of the combined resistance becomes 60Ω. 
         [0029]    The battery module control unit  31  has two CAN communication connecting portions  33   a  and  33   b  as described above, the two CAN communication connecting portions  33   a  and  33   b  are connected to each other by connection wires  34  in a daisy chain configuration (a configuration of serial connection). Each of the CAN communication connecting portions  33   b  of the battery module control units  31  connected to the battery pack control unit  230 , an upper controller, is connected to the CAN communication connecting portion  233  of the battery pack control unit  230  by the connection wire  36  in a bus configuration. 
         [0030]    Subsequently, it will be described about the parts connected in a daisy chain configuration. The CAN communication connecting portion  33   a  provided in one battery module control unit  31  and the CAN communication connecting portion  33   b  provided in the battery module control unit  31  of adjacent battery module  30  are connected by the connection wire  34  through the termination resistor  35 , thus communication between battery module control units  31  is performed. The termination resistor  35  is provided in the battery module  30 , specifically, only in one side of the CAN communication connecting portion  33  of each battery module control unit  31 . In other words, the input impedance on the CAN communication connecting portion  33   a  side is configured to be different from the input impedance on the CAN communication connecting portion  33   b  side, and the input impedance on the one side (the CAN communication connecting portion  33   b  side) is low. 
         [0031]    In this case, the resistance value of the termination resistor  35  is determined such that the resistance value of the termination resistor  35  has ½ value of the resistance value at the time when the termination resistors are attached to the both ends of the CAN communication connecting portions  33   a  and  33   b  (the combined resistance when the termination resistor of 120Ω is connected in parallel). That is, if the resistance value of the termination resistor  35  is set to 60Ω, it is possible to sufficiently restrict the signal reflection. 
         [0032]    In the case of connection in the daisy chain configuration, if the path of reflected signal reaches ¼ of the wavelength of the signal, it becomes a problem, but 1/50 of the wavelength of the signal is also considered in order to enhance reliability. In addition, in the case of digital communication (communication in a rectangular wave), many harmonics are included, thus it is necessary to consider the wavelength of the harmonics, especially, to reduce an influence of a fifth harmonic of a signal. For example, in the case of performing CAN communication (1 MHz is an upper limit), the length of 1/50 of a fifth harmonic is 1.2 m. Consequently, the length of the connection wire  34  is set to 1.2 m or less, thereby sufficiently suppressing signal reflection using the aforementioned termination resistor. 
         [0033]    In the above configuration, it is not necessary to select whether to mount the termination resistor, thereby providing a mounting method of a termination resistor in which it is not necessary to perform a setting operation for selecting mounting and add a circuit for selecting mounting. Also, in the present invention, it is possible to restrict the increase in the number of the termination resistor due to increase of the termination in the case of realizing a configuration having a daisy chain connection and a bus connection in the same circuit board (for example, herein referred to as the battery module control unit  31 ). 
         [0034]    Subsequently, it will be described about a circuit configuration of the battery system  201  using  FIG. 5 .  FIG. 5  is a diagram showing the battery system  201  to which the plurality of the battery blocks  50  having the battery packs  40  including the plurality of battery modules  30  are connected in parallel. 
         [0035]    First, it will be described about the configuration of the battery block  50 . The battery block  50  includes the battery pack  40 , a pre-charging circuit  55  connected in serial with the battery pack  40 . In addition, the battery blocks  50  are connected in parallel each other, connected to a positive electrode side of the inverter  104  through a switch body  251  and connected to a negative electrode side of the inverter  104  through a switch body  252 . 
         [0036]    A pre-charging circuit  55  includes a switch element  51 , and a resistor element  52  and a switch element  53  which are connected in parallel with the switch element  51 . When there is a variation in the charging states or voltages among the battery blocks  50 , the pre-charging circuit  55  turns a switch body  251  and a switch body  252  off in order to keep for the time being the duration when the switch element  51  is turned off and the switch element  53  is turned on, thereby lowering a variation in the charging states or voltages among the battery blocks  50  using cross current. 
         [0037]    Also, the battery block  50  has switch elements  54   a   1  ( 54   a ),  54   a   2  ( 54   a ) . . .  54   an  ( 54   a ) (where n is the number of battery packs  40  connected in parallel inside the battery block  50 ) connected in serial corresponding to the battery pack  40 . When there is a problem in each battery pack  40 , the switch element  54   a,  corresponding to the battery pack  40  having the problem, is made open, and thus the switch element  54   a  may be separated from other battery pack  40 . 
         [0038]    Subsequently, the outline diagram of the battery pack  40  relating to the present invention is shown in  FIG. 6 .  FIG. 6  is a diagram viewing the battery pack  40  from the back. The battery pack  40  includes the plurality of battery modules  30 , the battery pack control unit  230  to control the plurality of battery modules  30 , a module mounting plate  120  on which the plurality of battery modules  30  are mounted and a battery rack  110 . The battery modules  30  are mounted and arranged on the module mounting plate  120  to construct the module serial body  300 . In addition, the battery modules  30  are disposed separately each other in  FIG. 6 , but may be disposed closely each other. In the case where the battery modules  30  are disposed closely, it is easy to discharge the heat generated in the battery module  30  and the length of the connection wire  34  which connects the battery modules  30  each other may be short. Also, the connection wire  34  has a length of 1.2 m or less as described above. 
         [0039]    Using the above configuration, though connected in a daisy chain configuration, it is possible to sufficiently restrict signal reflection. 
         [0040]    On the other hand, among the battery modules  30  constituting the module serial body  300 , the side connected with the battery pack control unit  230  is connected through the connection wire  36  with the battery pack control unit  230  in a bus configuration. 
         [0041]    As described above, by using the present invention, it is possible to provide the battery system capable of suppressing communication delay while lowering the number of the parts of the termination resistors.