Abstract:
Provided is an installation structure for an electric power conversion device whereby the size of the device is reduced, and noise conducted to an external battery due to a switching operation is reduced. The electric power conversion device according to the present invention is therefore provided with an inverter circuit unit, a converter circuit unit for stepping up a voltage from an external battery and outputting to the inverter circuit unit or stepping down a power source voltage of the inverter circuit unit and outputting to a battery, and a capacitor package for storing a smoothing capacitor connected to an inverter circuit unit power source voltage and a converter circuit unit battery-side power source voltage. The capacitor package has a capacitor element, a negative electrode bus bar connected a negative electrode side of both the inverter circuit unit and of the converter circuit unit, a first positive electrode bus bar connected to a positive electrode of the inverter circuit unit, and a second positive electrode bus bar connected to a positive electrode of a converter circuit unit battery side, the first positive electrode bus bar facing one principal face of the negative electrode bus bar, and the second positive electrode bus bar being disposed in a position facing the other principal face of the negative electrode bus bar.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an electric power conversion device that is mounted on a vehicle and converts electric power, for example, and more specifically to a mounting structure of the same. 
       BACKGROUND ART 
       [0002]    Heretofore, there are already known an electric automobile that drives the vehicle with driving force from a dynamo-electric machine such as a motor, a so-called hybrid automobile including the dynamo-electric machine combined with an engine that is an internal combustion engine, and the like. These electric vehicles are generally mounted with an electric power conversion device including a DC/DC converter device that receives direct current power from a high voltage battery as a direct current power supply and converts the received direct current power into direct current power having a different voltage value, and outputs the direct current power, and an inverter device that receives the direct current power from the DC/DC converter, converts the received direct current power into alternating power, and drives a motor. 
         [0003]    In the electric power conversion device including the DC/DC converter and the inverter, more specifically, it is possible to aim to downsize the overall electric power conversion device by accommodating the DC/DC converter and the inverter in a shared casing to form a module. For example, in Patent Literature 1 below, a structure to realize the downsizing of a device is proposed in which a smoothing capacitor for a DC/DC converter provided on the input side of the DC/DC converter and a smoothing capacitor for an inverter provided on the input side of the inverter are accommodated in a shared capacitor package. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2007-174760 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0005]    However, in the above-described electric power conversion device according to the previously existing technique, since the mounting structure is adopted in which two systems using voltage sources different from each other, that is, the smoothing capacitor for the DC/DC converter and the smoothing capacitor for the inverter are accommodated in the shared package to downsize the overall device, different positive electrode bus bars for these two systems are disposed closely to each other. Therefore, problems arise in that noise caused by the switching operation of the inverter is superposed on the input side of the DC/DC converter and noise transmitted to an external battery is increased. 
         [0006]    When this transmission noise is carried through a cable connecting the electric power conversion device to the external battery (generally, the external battery is connected to the electric power conversion device using a shielded cable), the cable becomes an antenna to increase electromagnetic noise emitted to the inside and outside of a vehicle, and noise is caused on an on-vehicle radio. In a countermeasure, the noise can be decreased to some extent by additionally providing a filter on the external battery side of the DC/DC converter, for example. However, the effect is not always sufficient, and it is rather likely to cause an increase in manufacturing costs and an increase in the size of the device. 
         [0007]    Therefore, the present invention is made in consideration of the above-described problems in the previously existing technique, and it is an object of the present invention to provide an electric power conversion device that can realize the downsizing of the device and at the same time can decrease noise transmitted to an external battery due to noise caused by the switching operation of an inverter more specifically. 
       Solution to Problem 
       [0008]    In order to solve the problems, configurations described in claims, for example, are adopted. It is noted that the present invention includes a plurality of schemes to solve the problems. For one example, there is provided an electric power conversion device including a shared casing at a GND potential that accommodates: an inverter circuit unit that converts direct current power into alternating current power; a converter circuit unit that increases a voltage from an external battery and outputs the voltage to the inverter circuit unit or decreases a power supply voltage from the inverter circuit unit and outputs the voltage to the external battery; and a capacitor package that includes a smoothing capacitor element connected to a power supply voltage side of the inverter circuit unit and a smoothing capacitor element connected to a power supply voltage on a battery side of the converter circuit unit and integrally accommodates the elements. In the electric power conversion device, the capacitor package, together with the plurality of the smoothing capacitor elements, includes: a negative electrode bus bar connected to both of a negative electrode of the inverter circuit unit and a negative electrode side of the converter circuit unit; a first positive electrode bus bar connected to a positive electrode of the inverter circuit unit and connected to one capacitor of the smoothing capacitors; and a second positive electrode bus bar connected to a positive electrode on the battery side of the converter circuit unit and connected to the other capacitor of the smoothing capacitors. The first positive electrode bus bar is disposed at a position opposite to one principal face of the negative electrode bus bar, and the second positive electrode bus bar is disposed at a position opposite to the other principal face of the negative electrode bus bar and apart from the first positive electrode bus bar. 
       Advantageous Effects of Invention 
       [0009]    According to the present invention, noise coupling between an inverter device and a DC/DC converter device can be decreased, so that it is possible to provide an electric power conversion device that can realize the downsizing of the device and at the same time can decrease noise transmitted to an external battery due to noise caused by the switching operation of an inverter more specifically. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0010]      FIG. 1  is a circuit diagram of an exemplary schematic configuration of a motor drive system including an electric power conversion device according to an embodiment of the present invention. 
           [0011]      FIG. 2  is a diagram of the schematic configuration of the electric power conversion device according to the embodiment of the present invention. 
           [0012]      FIG. 3  is a partially exploded perspective view of the structure of bus bars in a capacitor package of the electric power conversion device. 
           [0013]      FIG. 4  is a cross sectional view (a cross section along line A-A′ in  FIG. 2  above) of the internal structure in the capacitor package of the electric power conversion device. 
           [0014]      FIG. 5  is a cross sectional view (a cross section along line A-A′ in  FIG. 2  above) of the internal structure in a capacitor package of an electric power conversion device according to another embodiment of the present invention. 
           [0015]      FIG. 6  is a cross sectional view (a cross section along line A-A′ in  FIG. 2  above) of the internal structure in a capacitor package of an electric power conversion device according to still another embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0016]    In the following, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
         [0017]      FIG. 1  is a circuit diagram of the schematic configuration of a motor drive system including an electric power conversion device according to an embodiment of the present invention. As illustrated in the drawing, the basic configuration includes an electric power conversion device having an external battery  1  that supplies direct current power, a converter  10 , and an inverter  40 , a motor generator  60  that generates power by the electric power conversion device or generates electric power (in the following, simply referred to as “a motor”), and a control circuit board  80  that drives and controls the electric power conversion device. In other words, for example, this motor drive system is mounted on an electric vehicle such as a hybrid automobile and an electric automobile, and the electric power conversion device has the power running operation and regeneration operation of the motor. 
         [0018]    In this motor drive system, in the power running operation, the converter  10  increases the direct current voltage of the external battery  1  that is a chargeable and dischargeable direct current power supply to a direct current voltage having a different value, and outputs the voltage to the inverter  40 . The inverter  40  converts the direct current power into alternating current power by PWM control, and outputs the alternating current power to the motor  60 . The motor  60  receives the alternating current power to rotate a rotor in the inside of the motor to be a load, and rotates the tires of the vehicle. Here, the motor  60  is a three-phase alternating current motor. 
         [0019]    On the other hand, in the regeneration operation, the alternating current power obtained by generating electric power using the motor  60  is converted into a direct current voltage by the inverter  40 , the direct current voltage is supplied to the converter  10 , the value of the direct current voltage is decreased by the converter  10 , and the direct current voltage is outputted to the external battery  1  for charging the external battery. 
         [0020]    It is noted that as illustrated in  FIG. 1 , the above-described converter  10  and the inverter  40  are configured to include semiconductor modules  13  and  43  having switching elements such as IGBTs, and the modules switch on and off the switching elements such as IGBTs using control signals from the control circuit board  80 . This control circuit board  80  controls the switching operation of the semiconductor modules based on signals from an external system, not illustrated. 
         [0021]    Next, in the following, the detailed configuration of the converter  10  will be described, and then two operating states of the converter, which are a voltage increase operation and a voltage decrease operation, will be further described. 
       &lt;Configuration and Operation of the Converter&gt; 
       [0022]    As apparent from  FIG. 1 , the converter  10  includes the semiconductor module  13 , a reactor  14 , and a converter smoothing capacitor C 1 . Moreover, the semiconductor module  13  includes a pair of switching elements Qa 0  and Qb 0 , and diodes Da 0  and Db 0  are connected in parallel with each other between the collectors and emitters of the switching elements Qa 0  and Qb 0 , respectively. The output end of the converter (the positive electrode side of the inverter  40 ) is connected to the collector side of the switching element Qa 0 , and one end of the reactor  14  and the collector side of the switching element Qb 0  are connected to the emitter side. Furthermore, the other end of the reactor  14  is connected to the positive electrode side of the external battery  1 , and the emitter side of the switching element Qb 0  is connected to a negative electrode bus bar  31  (the negative electrode side of the external battery  1 ). 
         [0023]    The converter  10  includes a voltage increase function that converts the value of a direct current voltage from the external battery  1  into the value of a direct current voltage higher than the value and outputs the direct current voltage to the inverter  40  and a voltage decrease function that converts a direct current voltage outputted from the inverter  40  to the converter  10  into a direct current voltage lower than the outputted direct current voltage and outputs the direct current voltage to the external battery  1  in the regeneration operation of the motor  60 . 
         [0024]    In the following, the voltage increase operation of the converter  10  will be described. In the converter  10 , when the switching element Qb 0  is turned on, a short circuit that connects the positive electrode side to the negative electrode side of the external battery  1  is formed through the external battery  1  and the reactor  14 , and energy is temporarily stored on the reactor  14  with a direct electric current carried through the circuit. When the switching element Qb 0  is switched from on to off in this state, the energy stored on the reactor  14  is charged on an inverter smoothing capacitor C 4  through the diode Da 0 . In the charging, the output voltage of the converter  10  can be increased more than the input voltage of the converter  10 . It is noted that in the voltage increase operation, the switching element Qa 0  is always off. The description above is the description of the operation as a voltage increase converter. 
         [0025]    Next, the voltage decrease operation of the converter  10  will be described. While the switching element Qa 0  is in the on state, in the converter  10 , a short circuit that connects the inverter smoothing capacitor C 4  and the reactor  14  to the positive electrode side of the external battery  1  is formed, and energy stored on the inverter smoothing capacitor C 4  by the regeneration operation of the motor  60  is temporarily stored on the reactor  14  while being charged on the external battery  1 . When the switching element Qa 0  is turned off in this state, a short circuit that connects the reactor  14  and the external battery  1  to the diode Db 0  is formed, a charge current is carried from the energy temporarily stored on the reactor  14  to the external battery. Therefore, the voltage value to the external battery  1  in the regeneration operation can be controlled by the ratio of on time occupied in one cycle of on and off time of the switching element Qa 0 , and the converter  10  also functions as a voltage decrease converter. It is noted that in the voltage decrease operation, the switching element Qb 0  is always off. Moreover, the converter smoothing capacitor C 1  is connected to the external battery side of the converter  10 . The converter smoothing capacitor C 1  absorbs ripples produced by switching the switching elements Qa 0  and Qb 0 . Furthermore, the converter smoothing capacitor C 1  absorbs a ripple current included in a power supply current inputted from the direct current external battery  1  to the converter  10 , and stabilizes the power supply current. 
         [0026]    Next, in the following, the configuration of the inverter  40  will be described in detail. 
       &lt;Configuration and Operation of the Inverter&gt; 
       [0027]    The inverter  40  includes the semiconductor module  43  and the inverter smoothing capacitor C 4 . The configuration of the semiconductor module  43  includes switching elements Qa 1 , Qa 2 , Qa 3 , Qb 1 , Qb 2 , and Qb 3  and diodes Da 1 , Da 2 , Da 3 , Db 1 , Db 2 , and Db 3 . 
         [0028]    The diodes are connected to the individual switching elements in parallel with each other; Qa 1  is connected to Da 1 , Qa 2  is connected to Da 2 , Qa 3  is connected to Da 3 , Qb 1  is connected to Db 1 , Qb 2  is connected to Db 2 , and Qb 3  is connected to Db 3 . 
         [0029]    The inverter positive electrode bus bar  41  is connected to the collector side of the switching elements Qa 1 , Qa 2 , and Qa 3 . On the other hand, the negative electrode bus bar  31  is connected to the emitter side of the switching elements Qb 1 , Qb 2 , and Qb 3 . Moreover, the emitter side of the switching elements Qa 1 , Qa 2 , and Qa 3  and the collector side of the switching elements Qb 1 , Qb 2 , and Qb 3  are connected to the motor  60 ; Qa 1  and Qb 1  are connected to the U-phase, Qa 2  and Qb 2  are connected to the V-phase, and Qa 3  and Qb 3  are connected to the W-phase. 
         [0030]    The inverter  40  can drive the motor  60  in which the switching on and off of the switching elements Qa 1 , Qa 2 , Qa 3 , Qb 1 , Qb 2 , and Qb 3  is controlled using the output direct current power of the converter  10  and three-phase alternating current power is generated and outputted to the motor  60  that the phase of an alternating current carried through the motor is varied individually in the U-, V-, and W-phases at an angle of 120°. 
         [0031]    Moreover, the inverter smoothing capacitor C 4  is connected to the output side of the converter  10  and the input side of the inverter, and the inverter smoothing capacitor absorbs ripples produced by switching the semiconductor module  43 . Furthermore, the inverter smoothing capacitor C 4  smoothes the output of the voltage increase converter  10 , and inputs a stabilized direct current power to the inverter  40 . 
       &lt;Filter&gt; 
       [0032]    As also illustrated in  FIG. 1 , the above-described converter  10  and the inverter  40  include filter capacitors C 2 , C 3 , and C 5 . C 2  is electrically connected to the positive electrode of the converter  10 , C 5  is electrically connected to the positive electrode of the inverter  40  and a ground, and C 3  is electrically connected to the negative electrode and the ground. The capacitors are mounted to decrease common mode noise carried through the positive electrodes and the negative electrodes, and bypass noise from the external battery  1  and noise from the converter  10  and the inverter  40  to the ground for preventing common mode noise from being transmitted to the external battery. Moreover, the capacitors also prevent common mode noise from the external battery  1  from being transmitted to the converter  10 . 
         [0033]    As also illustrated in  FIG. 1  described above, in the electric power conversion device, the filter capacitors are mounted on both of the converter  10  and the inverter  40 . Since the negative electrode bus bar  31  of the inverter  40  is electrically connected to the converter  10 , the filter capacitor C 3  for the negative electrode is a single capacitor by sharing capacitors for the converter  10  and the inverter  40 , so that downsizing can be intended by sharing components. However, in order to select the capacitance values of the filter capacitors for the individual systems, it is acceptable that the filter capacitor C 3  connected to the negative electrode is not shared, and is split for the converter  10  and the inverter  40  for mounting. 
         [0034]    The attached  FIG. 2  is the mounting structure of an electric power conversion device according to an example (a first example) of the present invention. As illustrated in  FIG. 2 , the converter  10  (the converter smoothing capacitor C 1  and the semiconductor module  13 ), the inverter  40  (the inverter smoothing capacitor C 4  and the semiconductor module  43 ), and the filter capacitors C 2 , C 3 , and C 5  are accommodated in a shared casing (a case at a GND potential)  101 , so that the downsizing of the electric power conversion device can be intended. Here, this casing  101  is formed of a conductive material such as a metal (aluminum, for example). Thus, the casing  101  also serves as a shield function that prevents electromagnetic noise from the electronic components accommodated in the inside of the casing from being propagated to the outside and prevents external electromagnetic noise from entering the accommodation space of the electronic components. The casing  101  is electrically connected to an earth on the vehicle side (a body chassis, for example), and functions as an electrical earth for the electric power conversion device. 
         [0035]    Moreover, although not illustrated in the drawing here, the casing (the case)  101  has a passage through which cooling water is carried, and the converter  10  and the inverter  40  accommodated in the casing  101  can be cooled with cooling water carried through the passage. 
         [0036]    Next, in the following, the detailed structure of a capacitor package of the electric power conversion device according to the example, that is, the detail of the capacitors and the bus bars accommodated in the package will be described with reference to the attached  FIGS. 3 and 4 . 
       Capacitor Package 
     First Example 
       [0037]    In this example, as illustrated in  FIGS. 3 and 4 , a plurality of film capacitors (in other words, a converter smoothing capacitor C 1 , an inverter smoothing capacitor C 4 , and filter capacitors C 2 , C 3 , and C 5 ) and parts of conductor plates electrically connected to the film capacitors (a converter positive electrode bus bar  11 , a negative electrode bus bar  31 , and an inverter positive electrode bus bar  41 ) are accommodated in a shared capacitor package  90  (see  FIG. 4 ) for sharing these capacitor components C 1 , C 2 , C 3 , C 4 , and C 5  as one package. Thus, the downsizing of the capacitor components can be intended, and the overall electric power conversion device can be downsized. Moreover, the number of parts can be decreased, so that the workability of the assembly of the device can also be improved. 
         [0038]    It is noted that as also apparent from  FIG. 3 , the converter positive electrode bus bar  11 , the negative electrode bus bar  31 , and the inverter positive electrode bus bar  41 , which are parts of the conductor plates, are formed of members in a plate (bar) shape made of an electric conductor such as copper, for example, and plate-shaped members  32  and  33  formed of an insulating material are inserted between the converter positive electrode bus bar  11  and the negative electrode bus bar  31  and between the negative electrode bus bar  31  and the inverter positive electrode bus bar  41 , respectively, for providing electrical insulation between the bus bars. Moreover, in these drawings, “” express electrical connecting portions, and “∘” express through holes, which are not electrically connected and are passed. 
         [0039]    In other words, as illustrated in these drawings, in the capacitor package  90 , the converter smoothing capacitor C 1  is electrically connected to the negative electrode bus bar  31  and the converter positive electrode bus bar  11 , and the inverter smoothing capacitor C 4  is electrically connected to the negative electrode bus bar  31  and the inverter positive electrode bus bar  41 . Furthermore, as also illustrated in  FIG. 1 , the negative electrode bus bar  31  of the inverter  40  is electrically connected to the converter  10 , and used as a shared conductor plate. 
         [0040]    As described above, in the electric power conversion device according to the example, since the overall device is downsized using the capacitor package  90  described above, such a structure is provided in which the positive electrode bus bars  11  and  41  of the two systems using different voltage sources are closely disposed. Therefore, capacitive or inductive noise coupling between the positive electrode bus bars  11  and  41  is increased, switching noise caused by the switching operation of the semiconductor module  43  is superposed on the input side of the converter (the converter positive electrode bus bar  11 ), and thus, noise transmitted to the external battery  1  is increased. Generally, the external battery  1  is connected to the converter  10  using a shielded cable or the like, for example. However, when noise transmitted to the external battery is returned to the electric power conversion device through a car body GND plane, for example, other than through the shielded cable, electromagnetic noise is emitted from this electric current loop, and noise is caused on an on-vehicle radio, for example. 
         [0041]    In order to decrease such noise transmitted to the external battery  1  (to reduce noise), a scheme can be considered that noise coupling described above is decreased using the structure of the bus bars of the two systems, or a scheme can be considered that noise transmitted to the external battery is prevented by the positional relationship of connection between the mounted filter capacitors C 2 , C 3 , and C 5  and feeding points  12  from the external battery. However, as already described, there are problems such as an increase in manufacturing costs and an increase in the size of the device. 
         [0042]    Therefore, in the present invention, in the electric power conversion device, more specifically inside the capacitor package  90  of the device, a structure is provided to decrease a so-called noise coupling that switching noise caused by the switching operation of the semiconductor module  43  is superposed on the converter positive electrode bus bar  11  through the inverter positive electrode bus bar  41 . In the following, the structure will be described in detail. 
         [0043]    First, as illustrated in  FIG. 4 , the converter positive electrode bus bar  11  is disposed at a position opposite to one principal face of the negative electrode bus bar  31 , and on the other hand, the inverter positive electrode bus bar  41  is disposed at a position opposite to the other principal face of the negative electrode bus bar  31 . Thus, electromagnetic coupling between the converter positive electrode bus bar  11  and the inverter positive electrode bus bar  41  is interrupted using the negative electrode bus bar  31 , so that noise coupling can be decreased. 
         [0044]    Subsequently, the positional relationship of connection between the filter capacitors C 2 , C 3 , and C 5  and the feeding points  12  from the external battery will be described. 
         [0045]    As illustrated in  FIG. 1 , the converter  10  and the inverter  40  include the filter capacitors C 2 , C 3 , and C 5 . In other words, the filter capacitors C 2 , C 3 , and C 5  bypass common mode noise to the ground through the filter capacitors before the common mode noise carried through the positive electrodes and the negative electrodes is transmitted to the external battery  1 , and thus the filter capacitors prevent noise from being transmitted to the external battery. 
         [0046]    Therefore, in the embodiment, it is preferable that the shared filter capacitor C 3  on the negative electrode side be disposed very closely to the feeding points  12  from the external battery as illustrated in  FIG. 4 . With this disposition, noise produced in the semiconductor module  13  and noise produced in the semiconductor module  43  are decreased by the operation of the capacitor C 3  before propagated to the external battery  1 . In contrast to this, in the case where for the connection position of the negative electrode bus bar  31  to the filter capacitor C 3  for the negative electrode in the capacitor package  90 , the position is disposed between the feeding points  12  from the external battery and the semiconductor module  13 , for example, switching noise caused by the semiconductor module  13  can be removed through the filter capacitors C 2  and C 3  before the switching noise is transmitted to the external battery. However, since the ESL (equivalent series inductance) of the filter capacitor C 3  for the negative electrode is increased with respect to switching noise caused by switching the semiconductor module  43 , the filter effect exerted by the filter capacitor C 3  is decreased, and it is not possible to achieve the initial purpose of the capacitor C 3 . 
         [0047]    Moreover, it is desirable to dispose the positive electrode side filter capacitor C 2  for the converter closely to C 3 . This is because in the case where the filter capacitors C 2  and C 3  are disposed separately from each other, that is, for example, in the case where the filter capacitor C 2  is disposed more closely to the semiconductor module  13  beyond the connecting point of C 3  to the negative electrode bus bar  31 , noise propagated through the negative electrode bus bar before decreased at the capacitor C 3  is coupled to the positive electrode bus bar after passed through the capacitor C 2  between the positive electrode bus bar and the negative electrode bus bar between the connecting points of the filter capacitors C 2  and C 3 . 
         [0048]    As described above in detail, the example includes the structure to decrease noise coupling that switching noise caused by the switching operation of the semiconductor module in the capacitor package is superposed on the converter positive electrode bus bar. However, the present inventors have found that noise propagation to the external battery is further decreased by decreasing various types of noise coupling including capacitive or inductive coupling (coupling) between the inverter positive electrode bus bar and the capacitor and between the converter positive electrode bus bar and the capacitor in the space of the capacitor package, that is, spatial propagation noise coupling, in addition to the structure to decrease noise coupling. In the following, the structure of a capacitor package including a structure for achieving this reduction will be described as second and third examples. 
       Second Example 
       [0049]    The attached  FIG. 5  is a structure in a capacitor package  90  according to the second example. In this example, in addition to the first example, as also illustrated in the drawing, a slit-shaped space is provided between the capacitor C 3  and the capacitor C 5  in the capacitor package  90 , and a shield wall  102  at the same potential as the potential (GND) of the casing  101  is inserted into the slit and disposed. With this structure, switching noise emitted from the capacitor C 4  and caused by switching the inverter  40  is blocked by the shield wall  102 , so that it is possible to further decrease noise coupling between the positive electrode bus bars of the converter  10  and the inverter  40 . 
       Third Example 
       [0050]    Moreover, the attached  FIG. 6  is a structure in a capacitor package  90  according to the third example. In this example, the smoothing capacitor components (C 1  and C 4 ) of the two systems are arranged and disposed in the capacitor package  90  similarly to the first example, and the negative electrode bus bar is disposed as a flat plate. However, as illustrated in  FIG. 6 , the components are disposed in such a manner that the negative electrode bus bar  31  is bent and the orientations of the smoothing capacitors C 1  and C 4  of the two systems connected to the corresponding positive electrode bus bar are directed to the opposite directions. Thus, the negative electrode bus bar  31  is disposed between these two smoothing capacitor cells, so that switching noise emitted from the inverter smoothing capacitor C 4  and caused by switching the inverter  40  can be interrupted at the negative electrode bus bar  31 . Moreover, the distance between the positive electrode bus bars  11  and  41  of the two systems can be increased by the height of the capacitor cells, so that it is possible to decrease noise coupled from the inverter  40  to the converter  10 , and it is possible to decrease noise transmitted to the external battery  1 . 
         [0051]    In the examples of the present invention, the description is made for an example of a vehicle system that drives a single motor as an example of the motor drive system including the electric power conversion device having the converter and the inverter mounted on the inside of the same casing. However, the present invention is not limited to the examples. In addition, the present invention can also be adapted to different system forms such as a system in which a plurality of inverters are connected in parallel with each other on the output side of the converter  40  to drive a plurality of motors, for example. Also in this case, the similar effects can be obtained. 
         [0052]    Moreover, it is acceptable that the foregoing embodiments are used independently or in combinations. This is because the effects of the embodiments can be exerted independently or in multiplication. Furthermore, the present invention is not limited to the above-described embodiments at all as long as the features are not impaired. 
       LIST OF REFERENCE SIGNS 
       [0000]    
       
           1  . . . External battery 
           10  . . . Converter 
           11  . . . Converter positive electrode bus bar 
           12  . . . Feeding point from external battery 
           13  . . . Converter semiconductor module 
           14  . . . Reactor 
           31  . . . Shared negative electrode bus bar 
           40  . . . Inverter 
           41  . . . Inverter positive electrode bus bar 
           43  . . . Inverter semiconductor module 
           60  . . . Motor generator 
           80  . . . Control circuit board 
           90  . . . Capacitor package 
           101  . . . Case (GND potential case) 
           102  . . . Shield wall 
         C 1  . . . Converter smoothing capacitor 
         C 2  . . . Converter positive filter capacitor 
         C 3  . . . Negative electrode side filter capacitor 
         C 4  . . . Inverter smoothing capacitor 
         C 5  . . . Inverter positive filter capacitor 
         Qa 0 , Qa 1 , Qa 2 , Qa 3 , Qb 0 , Qb 1 , Qb 2 , and Qb 3  . . . Switching element 
         Da 0 , Da 1 , Da 2 , Da 3 , Db 0 , Db 1 , Db 2 , and Db 3  . . . Diode