Patent Publication Number: US-2013241290-A1

Title: Filter circuit and bidirectional power conversion apparatus including thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of PCT international application Ser. No. PCT/JP2011/072621 filed on Sep. 30, 2011 which designates the United States, and which claims the benefit of priority from Japanese Patent Application No. 2010-250954, filed on Nov. 9, 2010; the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The present invention relates to a filter circuit and a bidirectional power conversion apparatus including thereof. 
     BACKGROUND 
     Examples of a power conversion apparatus that exchanges electrical energy bidirectionally include a power conversion apparatus that includes a converter that converts supplied power to DC power and an inverter that converts DC power to AC power, and a matrix converter apparatus configured by using bidirectional semiconductor switches each of which is configured by connecting two switching elements in antiparallel to each other and can be turned on and off independently for each direction. 
     One example of the power conversion apparatus is a current source inverter described in Japanese Patent No. 2755609. The current source inverter described in Japanese Patent No. 2755609 is composed of a converter that performs control of the magnitude of direct current while converting alternate current to direct current, a DC reactor that is connected to the DC output side of the converter and smoothes the ripple of the direct current, an inverter that is connected to the DC reactor and converts the direct current to AC voltage having a variable voltage and a variable frequency, and a load connected to the output side of the inverter, and includes a filter AC reactor and a filter capacitor, which absorb harmonics, on the input side and a filter capacitor, which absorbs harmonics, on the output side. 
     SUMMARY 
     A filter circuit according to the embodiment includes a first filter and a second filter. The first filter includes two first capacitors connected in series, two single-phase AC reactors connected to one ends of the two first capacitors, respectively, a second capacitor connected at one end to a neutral point of the two first capacitors, and a third capacitor connected between another ends of the two single-phase AC reactors. The second filter includes two common mode chokes, and two fourth capacitors connected in series between one ends of the two common mode chokes. Another end of the second capacitor is connected to a neutral point of the two fourth capacitors. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1  is a configuration diagram of a bidirectional power conversion apparatus according to a first embodiment of the present invention. 
         FIG. 2  is a configuration diagram of a bidirectional power conversion apparatus according to a second embodiment of the present invention. 
         FIG. 3  is a configuration diagram of a bidirectional power conversion apparatus according to a third embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments according to the present invention are described below with reference to the drawings. The same components are denoted by the same reference numerals and a duplicate explanation is omitted. 
     First Embodiment 
     First, the configuration of a bidirectional power conversion apparatus  100  according to the first embodiment of the present invention will be described with reference to  FIG. 1 . 
     As illustrated in  FIG. 1 , the bidirectional power conversion apparatus  100  according to the first embodiment of the present invention includes a DC voltage source  1 , an input filter  2  (second filter), a bidirectional power converter  3 , an output filter  4  (first filter), a DC voltage detector  5 , an AC voltage detector  6 , a switch  7  (first switch), a controller  8 , a commercial power source  9 , and a load  10 . For convenience sake, an explanation will be given where the DC voltage source  1  side of the bidirectional power converter  3  is the input side and the side of the bidirectional power converter  3  on which the commercial power source  9  and the load  10  connected via the switch  7  are present is the output side when the electrical energy is traveling from the DC voltage source  1  to the load  10 . 
     For the DC voltage source  1 , a battery that has a function as a DC voltage source is used. The input filter  2  is the second filter and includes common mode chokes L 3  and a plurality of capacitors C 4  connected in series. The common mode chokes L 3  are connected with the same polarity to the terminals of the DC voltage source  1 . The capacitors C 4  connected in series are connected between the terminals of the DC voltage source  1 . Furthermore, the neutral point n of the capacitors C 4  is connected to the connection point (neutral point n′) of capacitors C 1  connected in series, which will be described later, via a capacitor C 2 . 
     The bidirectional power converter  3  includes a matrix converter circuit  31  and a DC reactor L 1 , and moreover includes terminals P and N on the input side and terminals U and V on the output side. Furthermore, the matrix converter circuit  31  includes terminals R, S, and T on the input side, and the terminal P and the terminal N are connected to the terminal S and the terminal T, respectively. 
     The matrix converter circuit  31  includes IGBTs (Insulated Gate Bipolar Transistors) (S 1  to S 12 ) that are semiconductor switching elements and diodes (D 1  to D 12 ), and causes the IGBTs, each operating as a unidirectional switch, to function as six bidirectional switches (hereinafter, six switches are also referred to as first to sixth bidirectional switches) by connecting the IGBTs two by two in antiparallel to each other. One ends of the first and fourth bidirectional switches are connected to the DC reactor L 1  at the terminal R, one ends of the second and fifth bidirectional switches are connected to the positive polarity side (P) of the DC voltage input/output terminals (P, N) at the terminal S, and one ends of the third and sixth bidirectional switches are connected to the negative polarity side (N) of the DC voltage input/output terminals (P, N) at the terminal T. Moreover, the other ends of the first to third bidirectional switches are connected to the terminal U of the AC voltage input/output terminals (U, V) and the other ends of the fourth to sixth bidirectional switches are connected to the terminal V of the AC voltage input/output terminals (U, V). 
     One end of the DC reactor L 1  is connected to the positive polarity side of the DC voltage source  1  via one coil of the common mode chokes L 3  and the terminal S and the other end of the DC reactor L 1  is connected to one ends of the first and fourth bidirectional switches at the terminal R. 
     The matrix converter circuit  31  performs switching in accordance with a gate signal from the controller  8  and bidirectionally exchanges electrical energy (power conversion) between the DC voltage source  1  connected to the input side and the commercial power source  9  or the load  10  connected to the output side. 
     The bidirectional power converter  3  is configured as above and operates as the equivalent of a current source inverter that has a step-up function and is capable of regenerating power. 
     The output filter  4  is the first filter and includes the capacitors C 1  connected in series, the capacitor C 2 , a capacitor C 3 , and single-phase AC reactors L 2  that are two normal mode devices. The output filter  4  is such that the ends of the capacitors C 1  connected in series are connected to the terminals U and V, respectively, and the ends of the capacitor C 3  are connected to terminals A and B of the switch  7 , respectively. 
     One of the single-phase AC reactors L 2  is connected to the terminal U of the bidirectional power converter  3  and one end of the capacitor C 3  and the other of the single-phase AC reactors L 2  is connected to the terminal V and the other end of the capacitor C 3 . In other words, the configuration is such that both terminals of the single-phase AC reactors L 2  function as input/output terminals and the capacitors C 1  and the matrix converter circuit  31  are connected in parallel at one end side of the single-phase AC reactors L 2 . 
     The two single-phase AC reactors L 2  that are normal mode devices are arranged to the terminal U and the terminal V, respectively; therefore, for the common mode path, they function with an inductance that is half the inductance of the single-phase AC reactors L 2 . Thus, the inductance of the common mode chokes L 3  can be reduced and the effect of reducing conduction noise can also be obtained. 
     The capacitors C 1  connected in series are connected in parallel between the output terminals U and V of the bidirectional power converter  3 . Because the connection point (neutral point n′) of the capacitors C 1  is connected to the neutral point n of the capacitors C 4  via the capacitor C 2 , the capacitors C 1  function as a smoothing capacitor of the bidirectional power converter  3  and obtain an effect of reducing conduction noise and harmonics. 
     The DC voltage detector  5  detects the voltage of the DC voltage source  1  and outputs it to the controller  8  as a DC voltage signal Vdc. 
     The AC voltage detector  6  detects the voltage across both ends of the capacitor C 3  and outputs it to the controller  8  as a single-phase AC voltage signal Vuv. 
     The switch  7  includes the terminals A, B, and S 1  to S 4 . The switch  7  has a function of selectively connecting the commercial power source  9  or the load  10  and outputting the selected state information to the controller  8  as a switching signal SW 1  (state signal). When the switch  7  selects the commercial power source  9 , the switch  7  switches the terminal A to S 1  and switches the terminal B to S 3 , and, when the switch  7  selects the load  10 , the switch  7  switches the terminal A to S 2  and switches the terminal B to S 4 . The switching reference to the switch  7  is applied from a not-shown upper-level apparatus. 
     The controller  8  performs PWM control in accordance with a voltage reference signal Vref, the DC voltage signal Vdc, the single-phase AC voltage signal Vuv, and the switching signal SW 1  and outputs a gate signal to the bidirectional power converter  3 . The voltage reference signal Vref changes in conjunction with the switching signal SW 1 , and a DC voltage reference or a single-phase AC voltage reference is applied to the controller  8  from a not-shown upper-level apparatus. 
     With this configuration, the switch  7  is switched by the reference from the upper-level apparatus and its state information is input to the controller  8  as the switching signal SW 1 . When the controller  8  determines that the commercial power source  9  connected between the terminals S 1  and S 3  of the switch  7  is selected in accordance with the switching signal SW 1 , the controller  8  performs power conversion control in a direction in which the DC voltage source  1  is charged such that the voltage reference signal Vref matches the DC voltage signal Vdc. When the controller  8  determines that the load  10  connected between the terminals S 2  and S 4  of the switch  7  is selected, the controller  8  performs power conversion control in a direction in which the DC voltage source  1  is discharged such that the voltage reference signal Vref matches the single-phase AC voltage signal Vuv. 
     Moreover, in the bidirectional power conversion apparatus  100  according to the first embodiment, the capacitors C 4  connected in series are connected to the positive polarity side of the common mode chokes L 3  in  FIG. 1 ; however, the capacitors C 4  may be connected to the negative polarity side of the common mode chokes L 3  or the configuration may be such that the common mode chokes L 3  are omitted. 
     In this case, although the resonance frequency is affected due to the stray capacitance formed at the DC voltage source  1  or the inductance of the common mode path, similar effects are obtained for reduction of conduction noise and harmonics. 
     As described above, in the output filter  4  of the bidirectional power conversion apparatus  100  according to the present embodiment, components are commonalized by using the capacitors C 1  both for smoothing the ripple of the direct current and for reducing conduction noise and harmonics, and the impedance in the path that is a bypass for conduction noise is reduced by connecting the neutral points n and n′ via the capacitor C 2 . 
     In this manner, in the case of charging in which electrical energy travels from the commercial power source  9  to the DC voltage source  1 , the output filter  4  can reduce conduction noise and harmonics flowing to the commercial power source  9  side, and in the case of discharging in which electrical energy travels from the DC voltage source  1  to the load  10 , the output filter  4  can reduce conduction noise to the load  10 . 
     Second Embodiment 
     The bidirectional power conversion apparatus  100  according to the first embodiment of the present invention is described above. Next, a bidirectional power conversion apparatus  200  according to the second embodiment of the present invention will be described with reference to  FIG. 2 . 
     The bidirectional power conversion apparatus  200  according to the second embodiment is configured in a similar manner to the bidirectional power conversion apparatus  100  according to the first embodiment except that the bidirectional power conversion apparatus  200  includes a bidirectional power converter  3 ′ instead of the bidirectional power converter  3 . Therefore, in the following, for convenience&#39; sake of explanation, a duplicate explanation is appropriately omitted and points different from the first embodiment will be mainly described. 
     The bidirectional power converter  3 ′ includes a matrix converter circuit  32  and the DC reactor L 1 , and moreover includes the terminals P and N on the input side and the terminals U and V on the output side. Furthermore, the matrix converter circuit  32  includes the terminals R and S on the input side, and the terminal P is connected to the terminal R via the DC reactor L 1  and the terminal N is directly connected to the terminal S. 
     The matrix converter circuit  32  includes IGBTs (S 1  to S 8 ) that are semiconductor switching elements and diodes (D 1  to D 8 ) and causes the IGBTs, each operating as a unidirectional switch, to function as four bidirectional switches (hereinafter, four switches are also referred to as first to fourth bidirectional switches) by connecting the IGBTs two by two in antiparallel to each other. One ends of the first and third bidirectional switches are connected to the DC reactor L 1  at the terminal R and one ends of the second and fourth bidirectional switches are connected to the negative polarity side (N) of the DC voltage input/output terminals (P, N) at the terminal S. Moreover, the other ends of the first and second bidirectional switches are connected to the terminal U of the AC voltage input/output terminals (U, V) and the other ends of the third and fourth bidirectional switches are connected to the terminal V of the AC voltage input/output terminals (U, V). 
     One end of the DC reactor L 1  is connected to the positive polarity side of the DC voltage source  1  via one coil of the common mode chokes L 3  and the other end of the DC reactor L 1  is connected to one ends of the first and third bidirectional switches at the terminal R. 
     The matrix converter circuit  32  performs switching in accordance with a gate signal from the controller  8  and bidirectionally exchanges electrical energy (power conversion) between the DC voltage source  1  connected to the input side and the commercial power source  9  or the load  10  connected to the output side. 
     Although the bidirectional power conversion apparatus  200  according to the present embodiment is different from the bidirectional power conversion apparatus  100  according to the first embodiment in the above points, the bidirectional power conversion apparatus  200  operates as the equivalent of a current source inverter that has a step-up function and is capable of regenerating power in a similar manner to the bidirectional power conversion apparatus  100  according to the first embodiment and obtains a similar effect. 
     Third Embodiment 
     Next, a bidirectional power conversion apparatus  300  according to the third embodiment of the present invention will be described with reference to  FIG. 3 . 
     The bidirectional power conversion apparatus  300  according to the third embodiment is configured in a similar manner to the bidirectional power conversion apparatus  100  according to the first embodiment except that the bidirectional power conversion apparatus  300  includes a bidirectional power converter  3 ″ instead of the bidirectional power converter  3  and therefore additionally includes a switch  11  (second switch). Accordingly, in the following, for convenience&#39; sake of explanation, a duplicate explanation is appropriately omitted and points different from the first embodiment will be mainly described. 
     The bidirectional power converter  3 ″ includes a matrix converter circuit  33  and the DC reactor L 1 , and moreover includes the terminals P and N on the input side and the terminals U and V on the output side. Furthermore, the matrix converter circuit  33  includes the terminals R and S on the input side, and the terminal P is connected to the terminal R via the DC reactor L 1  and the terminal N is directly connected to the terminal S. 
     The matrix converter circuit  33  is configured by bridge-connecting four unidirectional switches (hereinafter, four switches are also referred to as first to fourth unidirectional switches) that include IGBTs (S 1  to S 4 ) and diodes (D 1  to D 4 ). One ends of the first and third unidirectional switches are connected to the DC reactor L 1  at the terminal R and one ends of the second and fourth unidirectional switches are connected to the negative polarity side (N) of the DC voltage input/output terminals (P, N) at the terminal S. Moreover, the other ends of the first and second unidirectional switches are connected to the terminal U of the AC voltage input/output terminals (U, V) and the other ends of the third and fourth unidirectional switches are connected to the terminal V of the AC voltage input/output terminals (U, V). 
     One end of the DC reactor L 1  is connected to one coil of the common mode chokes L 3  at the terminal P and the other end of the DC reactor L 1  is connected to one ends of the first and third unidirectional switches at the terminal R. 
     The switch  11  includes terminals A, B, and S 1  to S 4  and is provided between the DC voltage source  1  and the input filter  2 . The switch  11  has a function of reversing the polarity of the DC voltage source  1 , selecting the polarity and connecting the DC voltage source  1  to the input filter  2 , and outputting the state information on the selected polarity to the controller  8  as a switching signal SW 2  (state signal). The terminal A of the switch  11  is connected to the positive polarity side of the DC voltage source  1  and the terminal B of the switch  11  is connected to the negative polarity side of the DC voltage source  1 . When the switch  11  connects the DC voltage source  1  to the input filter  2  with positive polarity, the switch  11  switches the terminal A to S 1  and switches the terminal B to S 3 . When the switch  11  connects the DC voltage source  1  to the input filter  2  with reverse polarity, the switch  11  switches the terminal A to S 2  and switches the terminal B to S 4 . The switching reference to the switch  11  is applied from a not-shown upper-level apparatus. 
     The controller  8  performs PWM control in accordance with the voltage reference signal Vref, the DC voltage signal Vdc, the single-phase AC voltage signal Vuv, and the switching signals SW 1  and SW 2  and outputs a gate signal to the bidirectional power converter  3 ″. The voltage reference signal Vref changes in conjunction with the switching signals SW 1  and SW 2  and a DC voltage reference or a single-phase AC voltage reference is applied to the controller  8  from a not-shown upper-level apparatus. 
     Next, calculation of a gate signal performed by the controller  8  will be briefly described. 
     When the controller  8  determines that the load  10  and the DC voltage source  1  are connected with positive polarity and (potential Vu of terminal U potential Vv of terminal V) is satisfied in accordance with the switching signals SW 1  and SW 2  and the single-phase AC voltage signal Vuv, the controller  8  supplies the electrical energy of the DC voltage source  1  to the load  10  by the following operation. 
     Specifically, the controller  8  turns the first and second unidirectional switches on and accumulates the energy in the DC reactor L 1  by flowing current in the path of the positive polarity side of the DC voltage source  1 →the DC reactor L 1 →the diode (D 1 )→the IGBT (S 1 )→the diode (D 2 )→the IGBT (S 2 )→the negative polarity side of the DC voltage source  1 . 
     Next, the controller  8  turns the fourth unidirectional switch on. At this point, because the diode (D 4 ) is in the reverse biased state, current does not flow and the current path does not change. 
     Next, the controller  8  turns the second unidirectional switch off and turns the diode (D 4 ) on so as to flow the current in the path of the positive polarity side of the DC voltage source  1 →the DC reactor L 1 →the diode (D 1 )→the IGBT (S 1 )→the capacitors C 1  and the load  10 →the diode (D 4 )→the IGBT (S 4 )→the negative polarity side of the DC voltage source  1  with the DC reactor L 1  as a current source, thereby discharging the electrical energy in the DC reactor L 1  to the capacitors C 1  and the load  10 . 
     In this manner, the electrical energy in the DC voltage source  1  is supplied to the load  10 . 
     In the case where (potential Vu of terminal U&lt;potential Vv of terminal V), the controller  8  turns the third and fourth unidirectional switches on, then turns the second unidirectional switch on, and then turns the fourth unidirectional switch off, thereby supplying the electrical energy of the DC voltage source  1  to the load  10 . 
     Moreover, when the controller  8  determines that the commercial power source  9  and the DC voltage source  1  are connected with reverse polarity and (potential Vu of terminal U≧potential Vv of terminal V) is satisfied in accordance with the switching signals SW 1  and SW 2  and the single-phase AC voltage signal Vuv, the controller  8  supplies the electrical energy of the commercial power source  9  to the DC voltage source  1  by the following operation. 
     Specifically, the controller  8  turns the second and third unidirectional switches on, then turns the first unidirectional switch on, and then turns the third unidirectional switch on, thereby supplying the electrical energy of the commercial power source  9  to the DC voltage source  1 . 
     In the case where (potential Vu of terminal U&lt;potential Vv of terminal V), the controller  8  turns the first and fourth unidirectional switches on, then turns the third unidirectional switch on, and then turns the first unidirectional switch off, thereby supplying the electrical energy of the commercial power source  9  to the DC voltage source  1 . 
     Accordingly, even in the bidirectional power converter  3 ″, which includes four unidirectional switches configured by bridge-connecting them, electrical energy can be controlled bidirectionally by controlling the controller  8  in synchronization with the switch  7  and the switch  11 , i.e., a single-phase AC voltage obtained by stepping up the voltage of the DC voltage source  1  and performing power conversion thereon is supplied to the load  10  or the DC voltage obtained by stepping down the voltage of the commercial power source  9  and performing power conversion thereon is supplied to the DC voltage source  1 . 
     Although the bidirectional power conversion apparatus  300  according to the present embodiment is different from the bidirectional power conversion apparatus  100  according to the first embodiment in the above points, the bidirectional power conversion apparatus  300  operates as the equivalent of a current source inverter that has a step-up function and is capable of regenerating power in a similar manner to the bidirectional power conversion apparatus  100  according to the first embodiment and obtains a similar effect. 
     The embodiments of the present invention are described above. Various modifications may be made to the above embodiments by those skilled in the art without departing from the scope of the present invention and the above embodiments and the methods by the modified examples may be appropriately combined. In other words, it is obvious that such modified technologies and the like are also included in the technical scope of the present invention. 
     For example, an explanation is given of the unidirectional switching element in which the IGBT and the diode are connected in series; however, a reverse blocking IGBT (RB-IGBT: Reverse Blocking-Insulated Gate Bipolar Transistor) may be used as the unidirectional switching element and the diode may be omitted. If the RB-IGBT is applied to the bidirectional switch, the bidirectional module can be configured without using a reverse breakdown voltage protective diode that is needed for the IGBT. 
     REFERENCE SIGNS LIST