Power conversion device

Abstract

To downsize a power conversion device.SOLUTION: A switching circuit configured by switching arms 12U, 12V, and 12W is connected with at least one of both ends of each primary coil (18uv, 18vw, 18wu). A load circuit is connected with a positive electrode terminal 16p and a negative electrode terminal 16n as a pair of terminals of the switching circuit. Currents flow by switching in a plurality of current paths to taps of the primary coils corresponding to respective reactors (La, Lb, and Lc), via the respective primary coils, the switching circuit, an upper capacitor Cu, and the respective reactors, and thereby, the upper capacitor Cu is charged and discharged. Currents flow by switching in a plurality of current paths to the taps of the primary coils corresponding to the respective reactors, via the respective primary coils, the switching circuit, a lower capacitor Cd, and the respective reactors, and thereby, the lower capacitor Cd is charged and discharged.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a power conversion device, and more particularly to a device that performs power transmission by switching.

Background Art

[0002] Electric vehicles such as hybrid vehicles and electric vehicles are widely used. In recent years, research has been conducted on a technology called V2G (Vehicle to Grid) in which power is supplied from a battery mounted on an electric vehicle to a power system such as a commercial power supply system, and power is supplied from the power system to the battery. In V2G, a power conversion device that adjusts the power output from the battery and supplies it to the power system, or that adjusts the power supplied from the power system and outputs it to the battery is used. In addition, research has also been conducted on a technology called V2H (Vehicle to Home) in which power is supplied from a battery mounted on an electric vehicle to electrical equipment used in ordinary households, offices, etc. Also in V2H, a power conversion device is used in the power path between the battery and the electrical equipment. Power conversion devices include AC / DC power conversion devices that convert AC power to DC power or vice versa, and DC / DC power conversion devices that convert the level of DC voltage.

[0003] As a power conversion device, Patent Document 1 describes an insulated power conversion circuit system. In this system, two conversion circuits (switching circuits) including switching transistors are coupled by a transformer, and the transformer is used as a reactor for step-up or step-down. That is, the inductance appearing in the windings of the transformer is used for step-up or step-down.

[0004] The conversion circuit described in Patent Document 1 uses two arms, namely, a right arm and a left arm connected in parallel. Here, an arm refers to a circuit unit including two switching elements connected in series. A winding of a transformer is connected between the connection points of the two switching elements in one of the two arms and the connection points of the two switching elements in the other arm.

[0005] In a power conversion circuit system (power conversion device) as described in Patent Document 1, when the transmitted power is increased, the current flowing through each switching element and the voltage applied to each switching element increase. Therefore, it is necessary to increase the breakdown voltage and allowable current of each switching element, which may increase the manufacturing cost. In addition, the losses generated in each switching element may increase.

[0006] Therefore, as described in Non-Patent Document 1, there is one in which three arms connected in parallel are used. The connection points of the two switching elements in each arm constitute three-phase AC terminals, and three-phase transformer windings are connected to the three-phase AC terminals.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Non-Patent Documents

[0008]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] In the power conversion device shown in Patent Document 1 and Non-Patent Document 1, bidirectional power transmission between the primary side and the secondary side is performed by providing a phase difference between the switching of the switching circuit connected to the primary winding of the transformer and the switching of the switching circuit connected to the secondary winding. In such a power conversion device, when the transmitted power is increased, the current flowing through the transformer increases, and the losses generated in the transformer may increase, resulting in a decrease in transmission efficiency. Also, when designing to suppress the losses generated in the transformer, the transformer may become larger.

[0010] An object of the present invention is to miniaturize the power conversion device.

Means for Solving the Problems

[0011] The present invention Related ArtIt is a plurality of primary windings provided corresponding to a plurality of secondary windings, the plurality of primary windings each coupled to the corresponding secondary winding, and at least one of both ends of each of the primary windings is connected, and a switching circuit in which a load / power circuit is connected to a pair of terminals, which performs switching according to the voltage applied to each of the secondary windings, converts the alternating voltage appearing in each of the primary windings into a direct current voltage, and outputs it to the load / power circuit; a capacitor arm having both ends connected to the pair of terminals, the capacitor arm including a first capacitor and a second capacitor connected in series; and a plurality of reactors provided corresponding to the plurality of primary windings, each reactor being connected between the tap of the corresponding primary winding and the connection point of the first capacitor and the second capacitor. Current flows through the plurality of current paths reaching the tap of each primary winding through each primary winding, the switching circuit, the first capacitor, and each reactor by the switching, the first capacitor is charged and discharged, and from the tap of each primary winding, current flows through the plurality of current paths reaching each primary winding through the reactor corresponding to each primary winding, the second capacitor, and the switching circuit by the switching, the second capacitor is charged and discharged, and the voltage between the terminals of the capacitor arm and the current flowing through the load / power circuit are controlled by the switching.

[0012] Preferably, the switching circuit is a plurality of switching arms corresponding to the plurality of primary windings, each switching arm includes two switching elements connected in series, the switching circuit includes the plurality of switching arms, and the connection points of the two switching elements in each of the plurality of switching arms constitute a delta connection port for a multi-phase alternating voltage, and the plurality of primary windings are connected to the delta connection port.

[0013] Preferably, the switching circuit includes a plurality of switching arms corresponding to the plurality of primary windings, each switching arm including two switching elements connected in series, and the connection points of the two switching elements in each switching arm are connected to one end of the primary winding corresponding to each switching arm, and the other ends of the primary windings are commonly connected.

[0014] Further, the present invention includes a U-phase switching arm including a first switching element and a second switching element connected in series, a V-phase switching arm including a third switching element and a fourth switching element connected in series, a W-phase switching arm including a fifth switching element and a sixth switching element connected in series, a UV-phase primary winding coupled to an a-phase secondary winding, the UV-phase primary winding provided between the connection point of the first switching element and the second switching element and the connection point of the third switching element and the fourth switching element, a VW-phase primary winding coupled to a b-phase secondary winding, the VW-phase primary winding provided between the connection point of the third switching element and the fourth switching element and the connection point of the fifth switching element and the sixth switching element, a WU-phase primary winding coupled to a c-phase secondary winding, the WU-phase primary winding provided between the connection point of the fifth switching element and the sixth switching element and the connection point of the first switching element and the second switching element, a capacitor arm including a first capacitor and a second capacitor connected in series, an a-phase reactor provided between a tap of the UV-phase primary winding and the connection point of the first capacitor and the second capacitor, a b-phase reactor provided between a tap of the VW-phase primary winding and the connection point of the first capacitor and the second capacitor, and a c-phase reactor provided between a tap of the WU-phase primary winding and the connection point of the first capacitor and the second capacitor. The U-phase switching arm, the V-phase switching arm, the W-phase switching arm, and the capacitor arm are connected in parallel.

[0015] Further, the present invention includes a U-phase switching arm including a first switching element and a second switching element connected in series, a V-phase switching arm including a third switching element and a fourth switching element connected in series, a W-phase switching arm including a fifth switching element and a sixth switching element connected in series, a U-phase primary winding coupled to an a-phase secondary winding, one end of which is connected to a connection point of the first switching element and the second switching element, a V-phase primary winding coupled to a b-phase secondary winding, one end of which is connected to a connection point of the third switching element and the fourth switching element, V Phase a primary winding, a W-phase primary winding coupled to a c-phase secondary winding, one end of which is connected to a connection point of the fifth switching element and the sixth switching element, a capacitor arm including a first capacitor and a second capacitor connected in series, an a-phase reactor provided between a tap of the U-phase primary winding and a connection point of the first capacitor and the second capacitor, a b-phase reactor provided between a tap of the V-phase primary winding and a connection point of the first capacitor and the second capacitor, and a c-phase reactor provided between a tap of the W-phase primary winding and a connection point of the first capacitor and the second capacitor, wherein the other ends of the U-phase primary winding, the V-phase primary winding, and the W-phase primary winding are commonly connected, and the U-phase switching arm, the V-phase switching arm, the W-phase switching arm, and the capacitor arm are connected in parallel.

[0016] Preferably, the first switching element and the second switching element are alternately turned on and off, the third switching element and the fourth switching element are alternately turned on and off, the fifth switching element and the sixth switching element are alternately turned on and off, the voltage applied to the a-phase secondary winding changes in the order of positive, positive, 0, negative, negative, 0 in one cycle, the voltage applied to the b-phase secondary winding changes in the order of negative, 0, positive, positive, 0, negative in one cycle, and the voltage applied to the c-phase secondary winding changes in the order of 0, negative, negative, 0, positive, positive in one cycle. Accordingly, the on / off states of the first switching element, the on / off state of the third switching element, and the on / off state of the fifth switching element change in the order of (on, off, on), (on, off, off), (on, on, off), (off, on, off), (off, on, on), (off, off, on).

Advantages of the Invention

[0017] According to the present invention, the power conversion device can be miniaturized.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 3C

Figure 3D

Figure 4A

Figure 4B

Figure 5A

Figure 5B

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0019] Embodiments of the present invention will be described with reference to the accompanying drawings. The same reference numerals are given to the same components shown in a plurality of drawings, and the description thereof will be omitted. Terms indicating directions such as up, down, left, and right in this specification indicate the directions in the drawings. These terms indicating directions do not limit the posture when arranging each component. Further, unless otherwise specified, the voltage at both ends of each element is the voltage with the lower terminal in the circuit diagram set to 0 V. The terms primary winding and secondary winding in this specification are for convenience of explanation and do not limit the power transmission direction between the circuit connected to the primary winding and the circuit connected to the secondary winding.

[0020] FIG. 1 shows the configuration of a power conversion system 100 according to a first embodiment of the present invention. The power conversion system 100 includes a capacitor-split type power conversion device 10 and a power conversion device 40. The capacitor-split type power conversion device 10 includes a U-phase switching arm 12U, a V-phase switching arm 12V, a W-phase switching arm 12W, a capacitor arm 14C, a UV-phase primary winding 18uv, a VW-phase primary winding 18vw, a WU-phase primary winding 18wu, an a-phase reactor La, a b-phase reactor Lb, a c-phase reactor Lc, a positive terminal 16p, and a negative terminal 16n.

[0021] The U-phase switching arm 12U includes switching elements S1 and S2 (a first switching element and a second switching element) connected in series. The V-phase switching arm 12V includes switching elements S3 and S4 (a third switching element and a fourth switching element) connected in series. The W-phase switching arm 12W includes switching elements S5 and S6 (a fifth switching element and a sixth switching element) connected in series.

[0022] The capacitor arm 14C includes an upper capacitor Cu and a lower capacitor Cd (a first capacitor and a second capacitor) connected in series. The U-phase switching arm 12U, the V-phase switching arm 12V, the W-phase switching arm 12W, and the capacitor arm 14C are connected in parallel.

[0023] That is, the terminals on the side opposite to the switching element S2 of the switching element S1 (the upper terminal), the terminals on the side opposite to the switching element S4 of the switching element S3 (the upper terminal), and the terminals on the side opposite to the switching element S6 of the switching element S5 (the upper terminal) are connected. Also, the terminals on the side opposite to the switching element S1 of the switching element S2 (the lower terminal), the terminals on the side opposite to the switching element S3 of the switching element S4 (the lower terminal), and the terminals on the side opposite to the switching element S5 of the switching element S6 (the lower terminal) are connected. The upper parallel connection points and the lower parallel connection points of the U-phase switching arm 12U, the V-phase switching arm 12V, the W-phase switching arm 12W, and the capacitor arm 14C are connected to the positive terminal 16p and the negative terminal 16n, respectively.

[0024] For each switching element, an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) may be used. When an IGBT is used as the switching element, the series connection of two IGBTs means that the collector terminal of one IGBT is connected to the emitter terminal of the other IGBT. When a MOSFET is used as the switching element, the series connection of two MOSFETs means that the drain terminal of one MOSFET is connected to the source terminal of the other MOSFET. Also, each switching element includes a diode. When an IGBT is used in the switching element, the anode terminal is connected to the emitter terminal and the cathode terminal is connected to the collector terminal. When a MOSFET is used in the switching element, the anode terminal is connected to the source terminal and the cathode terminal is connected to the drain terminal.

[0025] Regarding the use of IGBTs, MOSFETs, etc. in each switching element, the fact that each switching element includes a diode, the definition of the series connection of the switching elements, and the definition of the parallel connection of the switching arms are the same for other switching elements described below.

[0026] Between the connection point of the switching elements S1 and S2 and the connection point of the switching elements S3 and S4, a UV-phase primary winding 18uv is connected. Between a tap at an intermediate point of the conductor forming the UV-phase primary winding 18uv and the connection point of the upper capacitor Cu and the lower capacitor Cd, an a-phase reactor La is connected. This tap may be a center tap at the midpoint of the conductor forming the UV-phase primary winding 18uv.

[0027] Between the connection points of the switching elements S3 and S4 and the connection points of the switching elements S5 and S6, a VW-phase primary winding 18vw is connected. Between a tap at an intermediate point of the conductor forming the VW-phase primary winding 18vw and the connection point of the upper capacitor Cu and the lower capacitor Cd, a b-phase reactor Lb is connected. This tap may be a center tap at the midpoint of the conductor forming the VW-phase primary winding 18vw.

[0028] Between the connection points of the switching elements S5 and S6 and the connection points of the switching elements S1 and S2, a WU-phase primary winding 18wu is connected. Between a tap at an intermediate point of the conductor forming the WU-phase primary winding 18wu and the connection point of the upper capacitor CU and the lower capacitor CL, a c-phase reactor Lc is connected. This tap may be a center tap at the midpoint of the conductor forming the WU-phase primary winding 18wu.

[0029] The power conversion device 10 includes an α-phase switching arm 22α, a β-phase switching arm 22β, a γ-phase switching arm 22γ, a capacitor C0, an a-phase secondary winding 20a, a b-phase secondary winding 20b, a c-phase secondary winding 20c, a positive electrode terminal 30p, and a negative electrode terminal 30n.

[0030] The α-phase switching arm 22α includes switching elements S7 and S8 connected in series. The β-phase switching arm 22β includes switching elements S9 and S10 connected in series, and the γ-phase switching arm 22γ includes switching elements S11 and S12 connected in series.

[0031] In the following description, the U-phase switching arm 12U, the V-phase switching arm 12V, and the W-phase switching arm 12W may be referred to as the switching arms 12U, 12V, and 12W, respectively. Similarly, the α-phase switching arm 22α, the β-phase switching arm 22β, and the γ-phase switching arm 22γ may be referred to as the switching arms 22α, 22β, and 22γ, respectively.

[0032] The switching arms 22α, 22β, and 22γ are connected in parallel. A capacitor C0 is connected in parallel to the switching arms 22α, 22β, and 22γ. That is, the capacitor C0 is connected between two parallel connection points of the switching arms 22α, 22β, and 22γ. The upper parallel connection point of the switching arms 22α, 22β, 22γ and the capacitor C0 is connected to the positive terminal 30p, and the lower parallel connection point of the switching arms 22α, 22β, 22γ and the capacitor C0 is connected to the negative terminal 30n.

[0033] An a-phase secondary winding 22a is connected between the connection points of the switching elements S7 and S8 and the connection points of the switching elements S9 and S10. A b-phase secondary winding 22b is connected between the connection points of the switching elements S9 and S10 and the connection points of the switching elements S11 and S12. A c-phase secondary winding 22c is connected between the connection points of the switching elements S11 and S12 and the connection points of the switching elements S7 and S8.

[0034] The a-phase secondary winding 20a is coupled to the UV-phase primary winding 18uv and constitutes a transformer Ta together with the UV-phase primary winding 18. The b-phase secondary winding 20b is coupled to the VW-phase primary winding 18vw and constitutes a transformer Tb together with the VW-phase primary winding 18vw. The c-phase secondary winding 20c is coupled to the WU-phase primary winding 18wu and constitutes a transformer Tc together with the WU-phase primary winding 18wu.

[0035] The two switching elements included in each of the switching arms 12U, 12V, 12W, 22α, 22β, and 22γ are turned on and off alternately. For example, when the switching element S1 included in the switching arm 12U switches from on to off, the switching element S2 switches from off to on. And when the switching element S1 switches from off to on, the switching element S2 switches from on to off. The same applies to the other switching arms 12V, 12W, 22α, 22β, and 22γ. That is, in FIG. 1, the switching elements drawn above and below one switching arm turn on and off alternately.

[0036] In the power conversion system 100, the transformers Ta, Tb, and Tc electrically insulate the capacitor-split type power conversion device 10 and the power conversion device 40. As a result, when one of the capacitor-split type power conversion device 10 and the power conversion device 40 is mounted on a device operated by a user, the insulation design of that device becomes easier.

[0037] FIG. 2 shows the relationship between the states of the respective switching elements and the voltages appearing at both ends of each secondary winding. In the six columns to the right of the columns labeled t1, t2,... t6 in FIG. 2, for the periods t1 to t6, the switching states of the upper switching elements S1, S3, and S5 included in the capacitor-split type power conversion device 10 and the upper switching elements S7, S9, and S11 included in the power conversion device 40, whether they are on or off, are shown. The symbol "1" shown in FIG. 2 means that the switching element is on, and the symbol "0" means that the switching element is off. In the power conversion system 100, the switching state with the periods t1 to t6 as one cycle is repeated. The lengths of the periods t1, t3, and t5 may be the same. Also, the lengths of the periods t2, t4, and t6 may be the same.

[0038] The switching element S1 turns on, on, on, off, off, off in sequence during the periods t1 to t6. The switching element S3 turns off, off, on, on, on, off in sequence during the periods t1 to t6. The switching element S5 turns on, off, off, off, on, on in sequence during the periods t1 to t6. Thus, the switching phase of the switching element S3 lags behind that of the switching element S1 by one-third of a cycle. The switching phase of the switching element S5 lags behind that of the switching element S3 by one-third of a cycle, and the switching phase of the switching element S1 lags behind that of the switching element S5 by one-third of a cycle. The switching elements S7, S9, and S11 perform switching synchronized with the switching elements S1, S3, and S5, respectively, and have the same switching state.

[0039] In the three right columns of FIG. 2, for the periods t1 to t6, it is shown whether the voltages vta appearing at both ends of the a-phase secondary winding 20a, the voltage vtb appearing at both ends of the b-phase secondary winding 20b, and the voltage vtc appearing at both ends of the c-phase secondary winding 20c are positive, 0, or negative. The symbol "0" indicates that the voltage becomes 0. The symbols "+" and "-" indicate that the voltage becomes positive and negative, respectively. The voltage vtb lags behind the voltage vta by one-third of a cycle. The voltage vtc lags behind the voltage vtb by one-third of a cycle, and the voltage vta lags behind the voltage vtc by one-third of a cycle.

[0040] The voltage vta becomes positive, positive, 0, negative, negative, 0 in sequence during the periods t1 to t6. The voltage vtb becomes negative, 0, positive, positive, 0, negative in sequence during the periods t1 to t6. The voltage vtc becomes 0, negative, negative, 0, positive, positive in sequence during the periods t1 to t6.

[0041] Thus, as the voltage applied to the a-phase secondary winding 20a changes in the order of positive, positive, 0, negative, negative, 0, the voltage applied to the b-phase secondary winding 20b changes in the order of negative, 0, positive, positive, 0, negative, and the voltage applied to the c-phase secondary winding 20c changes in the order of 0, negative, negative, 0, positive, positive, the switching states of the respective switching elements change as follows. The on / off states of the switching element S1, the on / off state of the switching element S3, and the on / off state of the switching element S5 change in the order of (101), (100), (110), (010), (011), (001). That is, the on / off state of the switching element S1, the on / off state of the switching element S3, and the on / off state of the switching element S5 change in the order of (on, off, on), (on, off, off), (on, on, off), (off, on, off), (off, on, on), (off, off, on).

[0042] Figures 3A to 3D show the currents flowing through the a-phase secondary winding 20a and the UV-phase primary winding 18uv in each period. The circled marks around the switching elements in each figure indicate that the switching elements are on. A power supply circuit 34 is connected to the positive terminal 30p and the negative terminal 30n of the power conversion device 40. A load circuit 32 is connected to the positive terminals 16p and 16n of the capacitor-divided power conversion device 10.

[0043] Figure 3A shows the a-phase input current Ia flowing through the a-phase secondary winding 20a and the UV-phase output current Iuv flowing through the UV-phase primary winding 18uv in periods t1 and t2. The a-phase input current Ia flows in from the positive terminal 30p, passes through the switching element S7, the a-phase secondary winding 20a, and the switching element S10 in sequence, and flows out from the negative terminal 30n. The UV-phase output current Iuv flows in from the negative terminal 16n, passes through the switching element S4, the UV-phase primary winding 18uv, and the switching element S1 in sequence, and flows out from the positive terminal 16p. As a result, the DC power input from the positive terminal 30p and the negative terminal 30n is output from the positive terminal 16p and the negative terminal 16n.

[0044] Figure 3B shows the a-phase zero-period current Ia0 and the UV-phase zero-period current Iuv0 during period t3. The a-phase zero-period current Ia0 flows into the switching element S9 from the a-phase secondary winding 20a, and flows through a loop that returns from the switching element S9 through the switching element S7 to the a-phase secondary winding 20a. The UV-phase zero-period current Iuv0 flows into the switching element S1 from the UV-phase primary winding 18uv, and flows through a loop that returns from the switching element S1 through the switching element S3 to the UV-phase primary winding 18uv.

[0045] Figure 3C shows the a-phase input current Ia and the UV-phase output current Iuv during periods t4 and t5. The a-phase input current Ia flows in from the positive terminal 30p, and flows out from the negative terminal 30n through the switching element S9, the a-phase secondary winding 20a, and the switching element S8 in sequence. The UV-phase output current Iuv flows in from the negative terminal 16n, and flows out from the positive terminal 16p through the switching element S2, the UV-phase primary winding 18uv, and the switching element S3 in sequence. Thereby, the DC power input from the positive terminal 30p and the negative terminal 30n is output from the positive terminal 16p and the negative terminal 16n.

[0046] Figure 3D shows the a-phase zero-period current Ia0 and the UV-phase zero-period current Iuv0 during period t6. The a-phase zero-period current Ia0 flows into the switching element S8 from the a-phase secondary winding 20a, and flows through a loop that returns from the switching element S8 through the switching element S10 to the a-phase secondary winding 20a. The UV-phase zero-period current Iuv0 flows into the switching element S4 from the UV-phase primary winding 18uv, and flows through a loop that returns from the switching element S4 through the switching element S2 to the UV-phase primary winding 18uv.

[0047] As shown in FIGS. 3A and 3C, during periods t1 and t2, and during periods t4 and t5, the DC power input from the positive terminal 30p and the negative terminal 30n is output from the positive terminal 16p and the negative terminal 16n via the transformer Ta. According to the switching method shown in FIG. 2, from the three-phase symmetry of the structure and the three-phase symmetry on the time axis of the switching method, during periods t3 and t4, and during periods t6 and t1, the DC power input from the positive terminal 30p and the negative terminal 30n is output from the positive terminal 16p and the negative terminal 16n via the transformer Tb. Also, during periods t5 and t6, and during periods t2 and t3, the DC power input from the positive terminal 30p and the negative terminal 30n is output from the positive terminal 16p and the negative terminal 16n via the transformer Tc.

[0048] The a-phase zero-period current Ia0 flowing through the a-phase secondary winding 20a and the UV-phase zero-period current Iuv0 flowing through the UV-phase primary winding 18uv during periods t3 and t6 do not contribute to the power transmitted from the positive terminal 30p and the negative terminal 30n to the positive terminal 16p and the negative terminal 16n. Alternatively, the influence of the a-phase zero-period current Ia0 and the UV-phase zero-period current Iuv0 on such transmitted power is negligible.

[0049] Similarly, during periods t5 and t2, the b-phase zero-period current Ib0 flows through the b-phase secondary winding 20b due to both the switching elements S9 and S11 being turned on and both the switching elements S10 and S12 being turned on. Also, during periods t5 and t2, the VW-phase zero-period current Ivw0 flows through the VW-phase primary winding 18vw due to both the switching elements S3 and S5 being turned on and the switching elements S4 and S6 being turned on.

[0050] Similarly, during periods t1 and t4, the zero-period current Ic0 of the c-phase due to both switching elements S7 and S11 being turned on and both switching elements S8 and S12 being turned on flows through the c-phase secondary winding 20c. Also, during periods t1 and t4, the zero-period current Iwu0 of the WU-phase due to both switching elements S1 and S5 being turned on and both switching elements S2 and S6 being turned on flows through the WU-phase primary winding 18wu.

[0051] Each zero-period current does not contribute to the power transmitted from the positive terminal 30p and the negative terminal 30n to the positive terminal 16p and the negative terminal 16n. Alternatively, the influence of each zero-period current on such transmitted power is negligible. The zero-period current generates an induced electromotive force in each phase reactor. The voltages across the upper capacitor Cu and the lower capacitor Cd are maintained by the induced electromotive force generated in each phase reactor and the voltage appearing across each phase primary winding.

[0052] The currents that contribute to the power transmitted from the positive terminal 30p and the negative terminal 30n to the positive terminal 16p and the negative terminal 16n do not flow through the a-phase reactor La, the b-phase reactor Lb, and the c-phase reactor Lc theoretically. Therefore, the influence of the a-phase reactor La, the b-phase reactor Lb, and the c-phase reactor Lc on the transmitted power is small.

[0053] FIG. 4A and FIG. 4B show the load current IL flowing through the load circuit 32, the first capacitor current Ic1 flowing through the upper capacitor Cu, and the second capacitor current Ic2 flowing through the lower capacitor Cd during periods t1 and t2. However, these figures focus on the first capacitor current Ic1 and the second capacitor current Ic2 flowing through the UV-phase primary winding 18uv, the U-phase switching arm 12U, and the V-phase switching arm 12V.

[0054] Figure 4A shows the load current IL, the first capacitor current Ic1, and the second capacitor current Ic2 during periods t1 and t2. During periods t1 and t2, a positive voltage appears across the UV-phase primary winding 18uv. The first capacitor current Ic1 flows from the U-phase switching arm 12U side (upper UV-phase primary winding) above the tap of the UV-phase primary winding 18uv, through the switching element S1, the upper capacitor Cu, and the a-phase reactor La in sequence, and returns to the tap of the UV-phase primary winding 18uv. Also, the second capacitor current Ic2 flows from the tap of the UV-phase primary winding 18uv, through the a-phase reactor La, the lower capacitor Cd, and the switching element S4 in sequence, and returns to the V-phase switching arm 12V side (lower UV-phase primary winding) below the tap of the UV-phase primary winding 18uv. Further, the load current IL flows through the lower capacitor Cd, the upper capacitor Cu, and the load circuit 32 in sequence. The load current IL flows due to the discharge of the upper capacitor Cu and the lower capacitor Cd. The upper capacitor Cu is charged by the first capacitor current Ic1 and the lower capacitor Cd is charged by the second capacitor current Ic2 by an amount of charge lost due to the discharge. Thereby, the voltage between the positive terminal 16p and the negative terminal 16n is maintained.

[0055] FIG. 4B shows the load current IL, the first capacitor current Ic1, and the second capacitor current Ic2 during periods t4 and t5. During periods t4 and t5, a negative voltage appears across the UV-phase primary winding 18uv. The first capacitor current Ic1 flows from the lower UV-phase primary winding, through the switching element S3, the upper capacitor Cu, and the a-phase reactor La in sequence, and returns to the tap of the UV-phase primary winding 18uv. Also, the second capacitor current Ic2 flows from the tap of the UV-phase primary winding 18uv, through the a-phase reactor La, the lower capacitor Cd, and the switching element S2, and returns to the upper UV-phase primary winding. Similar to periods t1 and t2, during periods t4 and t5, the load current IL flows due to the discharge of the upper capacitor Cu and the lower capacitor Cd. The upper capacitor Cu is charged by the first capacitor current Ic1 and the lower capacitor Cd is charged by the second capacitor current Ic2 by an amount of charge lost due to the discharge.

[0056] The first capacitor current Ic1 and the second capacitor current Ic2 flowing through the a-phase reactor La are in opposite directions. Therefore, the current flowing through the a-phase reactor La to contribute to the charging or discharging of the upper capacitor Cu and the lower capacitor Cd is very small or zero. Therefore, even when the current flowing through the load circuit 32 is large and the charging and discharging currents of the upper capacitor Cu and the lower capacitor Cd are large, it is not necessarily required to increase the inductance of the a-phase reactor La.

[0057] Due to the three-phase symmetry on the time axis of the operations of the U-phase switching arm 12U, the V-phase switching arm 12V, and the W-phase switching arm 12W, the first capacitor current Ic1 and the second capacitor current Ic2 similar to those in FIG. 4 flow through the VW-phase primary winding 12vw, the V-phase switching arm 12V, and the W-phase switching arm 12W with a delay of one-third of a period. Further, the first capacitor current Ic1 and the second capacitor current Ic2 similar to those in FIG. 4 flow through the WU-phase primary winding 18wu, the W-phase switching arm 12W, and the U-phase switching arm 12U with a delay of two-thirds of a period.

[0058] For charging or discharging the upper capacitor Cu and the lower capacitor Cd, the current flowing through each of the a-phase reactor La, b-phase reactor Lb, and c-phase reactor Lc is minute or zero. Therefore, regardless of the power input and output at the positive terminal 16p and the negative terminal 16n, the inductance of the a-phase reactor La, b-phase reactor Lb, and c-phase reactor Lc may be reduced. As a result, the a-phase reactor La, b-phase reactor Lb, and c-phase reactor Lc are miniaturized, and the capacitor-split type power conversion device 10 is miniaturized.

[0059] Also, in the power conversion system 100, there may be no phase difference between the switching of the capacitor-split type power conversion device 10 and the switching of the power conversion device 40. As a result, the power losses generated in the transformers Ta, Tb, and Tc are reduced.

[0060] In FIGS. 5A (t1) to (t3), for periods t1 to t3 respectively, the load current IL, the first capacitor current (IU + , IV + ) and the second capacitor current (IV - , IW - ) are shown. In FIGS. 5B (t4) to (t6), for periods t4 to t6 respectively, the load current IL, the first capacitor current (IV + , IW + ) and the second capacitor current (IU - , IV - ) are shown. However, these figures focus on the currents flowing through the upper UV-phase primary winding, the upper VW-phase primary winding, and the upper WU-phase primary winding among the first capacitor current and the second capacitor current.

[0061] The first capacitor current and the second capacitor current shown in these figures are currents that contribute to the power transmission to the load circuit 32. These figures show in detail the currents flowing through the positive terminal 16p and the negative terminal 16n shown in FIGS. 3A to 3D, including the currents for charging and discharging the upper capacitor Cu and the lower capacitor Cd.

[0062] The first capacitor current will be described. During periods t1 and t2, the U-phase first capacitor current IU flows from the upper UV-phase primary winding through the switching element S1, the upper capacitor Cu, and the a-phase reactor La in sequence, and returns to the tap of the UV-phase primary winding 18uv. + During periods t3 and t4, the V-phase first capacitor current IV flows from the upper VW-phase primary winding through the switching element S3, the upper capacitor Cu, and the b-phase reactor Lb in sequence, and returns to the tap of the VW-phase primary winding 18vw. + During periods t5 and t6, the W-phase first capacitor current IW flows from the upper WU-phase primary winding through the switching element S5, the upper capacitor Cu, and the c-phase reactor Lc in sequence, and returns to the tap of the WU-phase primary winding 18wu. + flows.

[0063] The second capacitor current will be described. During periods t2 and t3, the W-phase second capacitor current IW flows from the tap of the WU-phase primary winding 18wu through the c-phase reactor Lc, the lower capacitor Cd, and the switching element S6 in sequence, and returns to the upper WU-phase primary winding. - During periods t4 and t5, the U-phase second capacitor current IU flows from the tap of the UV-phase primary winding 18uv through the a-phase reactor La, the lower capacitor Cd, and the switching element S2 in sequence, and returns to the upper UV-phase primary winding. - During periods t6 and t1, the V-phase second capacitor current IV flows from the tap of the VW-phase primary winding 18vw through the b-phase reactor Lb, the lower capacitor Cd, and the switching element S4 in sequence, and returns to the upper VW-phase primary winding. - flows.

[0064] During periods t1 to t6, in order, the voltages across both ends of the WU-phase primary winding 18wu, VW-phase primary winding 18vw, UV-phase primary winding 18uv, WU-phase primary winding wu, VW-phase primary winding vw, and UV-phase primary winding uv are zero. The first capacitor current and the second capacitor current do not flow through the windings with zero voltage across both ends. Although not shown in FIGS. 5A and 5B, a zero-period current such as the a-phase zero-period current Ia0 shown in FIGS. 3B and 3D flows through the windings with zero voltage across both ends. The zero-period current generates an induced electromotive force in each phase reactor. The voltages across both ends of the upper capacitor Cu and the lower capacitor Cd are maintained by the induced electromotive force generated in each phase reactor and the voltage appearing across each phase primary winding.

[0065] The load current IL flows due to the discharge of the upper capacitor Cu and the lower capacitor Cd. The upper capacitor Cu is charged by the first capacitor current and the lower capacitor Cd is charged by the second capacitor current by an amount equal to the charge lost due to the discharge. That is, during period t1, the upper capacitor Cu is charged by the U-phase first capacitor current IU + and the lower capacitor Cd is charged by the V-phase second capacitor current IV - . During period t2, the upper capacitor Cu is charged by the U-phase first capacitor current IU + and the lower capacitor Cd is charged by the W-phase second capacitor current IW - . During period t3, the upper capacitor Cu is charged by the V-phase first capacitor current IV + and the lower capacitor Cd is charged by the W-phase second capacitor current IW - . During period t4, the upper capacitor Cu is charged by the V-phase first capacitor current IV + and the lower capacitor Cd is charged by the U-phase second capacitor current IU - . During period t5, the upper capacitor Cu is charged by the W-phase first capacitor current IW + and the lower capacitor Cd is charged by the U-phase second capacitor current IU - . During period t6, the upper capacitor Cu is charged by the W-phase first capacitor current IW +The upper capacitor Cu is charged by it, and the V-phase second capacitor current IV - The lower capacitor Cd is charged by it.

[0066] In the above, the case where the load circuit 32 is connected to the positive terminal 16p and the negative terminal 16n has been described. A power supply circuit 34 that supplies power to the capacitor-divided power conversion device 10 may be connected to the positive terminal 16p and the negative terminal 16n. When the power supply circuit 34 is connected to the positive terminal 16p and the negative terminal 16n, the load circuit 32 is connected to the positive terminals 30p and 30n. In this case, the upper capacitor Cu and the lower capacitor Cd are charged by the power output from the power supply circuit 34. Only the charged amount of charge, the upper capacitor Cu is discharged by the first capacitor current, the lower capacitor Cd is discharged by the second capacitor current, and the voltage between the positive terminal 16p and the negative terminal 16n is maintained.

[0067] As described above, the capacitor-divided power conversion device 10 includes a plurality of primary windings 18uv, 18vw, and 18wu provided corresponding to the plurality of secondary windings 20a, 20b, and 20c. The plurality of primary windings 18uv, 18vw, and 18wu are respectively coupled to the plurality of secondary windings 20a, 20b, and 20c to form transformers Ta, Tb, and Tc.

[0068] At least one of both ends of each primary winding (18uv, 18vw, 18wu) is connected to the switching circuit 12 formed by the U-phase switching arm 12U, the V-phase switching arm 12V, and the W-phase switching arm 12W. Further, the load / power supply circuit is connected to the positive terminal 16p and the negative terminal 16n as a pair of terminals of the switching circuit 12. Here, the load / power supply circuit refers to a load circuit 32, a power supply circuit 34, or a circuit that operates as the load circuit 32 or the power supply circuit 34 according to the operating situation. The circuit that operates as the load circuit 32 or the power supply circuit 34 according to the operating situation includes, for example, a circuit including a motor generator.

[0069] The switching circuit 12 performs switching according to the voltage applied to each secondary winding (20a, 20b, 20c), converts the alternating voltage appearing in each primary winding into a direct current voltage, and outputs it to the load / power supply circuit. The capacitor-divided power conversion device 10 includes a capacitor arm 14C with both ends connected to the positive terminal 16p and the negative terminal 16n. The capacitor arm 14C includes an upper capacitor Cu and a lower capacitor Cd as a first capacitor and a second capacitor connected in series.

[0070] The capacitor-divided power conversion device 10 includes an a-phase reactor La, a b-phase reactor Lb, and a c-phase reactor Lc as three reactors corresponding to the primary windings 18uv, 18vw, and 18wu. Each reactor (La, Lb, Lc) is connected between the tap of the corresponding primary winding and the connection point of the upper capacitor Cu and the lower capacitor Cd.

[0071] Through each primary winding, the switching circuit 12, the upper capacitor Cu, and each reactor, current flows through a plurality of current paths leading to the tap of each primary winding due to the switching of the switching circuit 12, and the upper capacitor Cu is charged and discharged. Also, from the tap of each primary winding, through the reactor corresponding to each primary winding, the lower capacitor Cd, and the switching circuit 12, current flows through a plurality of current paths leading to each primary winding due to switching, and the lower capacitor Cd is charged and discharged. Then, the voltage between the terminals of the capacitor arm 14C and the current flowing through the load / power supply circuit are controlled by the switching of the switching circuit 12.

[0072] The operation focusing on the charging and discharging of the capacitors will be described with reference to FIG. 6. FIG. 6(a) shows the first capacitor current Ic1 and the second capacitor current Ic2 during periods t1 and t2. During periods t1 and t2, the first capacitor current Ic1 flows from the tap of the UV-phase primary winding 18uv, through the upper UV-phase primary winding, the switching element S1, the upper capacitor Cu, and the a-phase reactor La in sequence, and then returns to the tap of the UV-phase primary winding 18uv. Also, the second capacitor current Ic2 flows from the tap of the UV-phase primary winding 18uv, through the lower UV-phase primary winding, the switching element S4, the lower capacitor Cd, and the a-phase reactor La in sequence, and then returns to the tap of the UV-phase primary winding 18uv. During periods t1 and t2, the upper capacitor Cu is charged and the lower capacitor Cd is discharged.

[0073] FIG. 6(b) shows the first capacitor current Ic1 (zero-period current) during period t3. During period t3, after the first capacitor current Ic1 shown in FIG. 6(a) decreases to 0, the flowing direction becomes reversed. That is, the first capacitor current Ic1 flows from the tap of the UV-phase primary winding 18uv, through the a-phase reactor La, the upper capacitor Cu, the switching element S1, and the upper UV-phase primary winding in sequence, and then returns to the tap of the UV-phase primary winding 18uv. Also, the first capacitor current Ic1 flows from the tap of the UV-phase primary winding 18uv, through the a-phase reactor La, the upper capacitor Cu, the switching element S3, and the lower UV-phase primary winding in sequence, and then returns to the tap of the UV-phase primary winding 18uv. During period t3, the second capacitor current Ic2 becomes 0, and the upper capacitor Cu changes from the charged state to the discharged state. The voltages across both the upper capacitor Cu and the lower capacitor Cd are determined by the induced electromotive force generated in the a-phase reactor La and the voltage appearing in the UV-phase primary winding 18uv.

[0074] Fig. 6(c) shows the first capacitor current Ic1 and the second capacitor current Ic2 during periods t4 and t5. During periods t4 and t5, the first capacitor current Ic1 flows from the tap of the UV-phase primary winding 18uv, through the a-phase reactor La, the upper capacitor Cu, the switching element S3, and the lower UV-phase primary winding in sequence. Also, the second capacitor current Ic2 flows from the tap of the UV-phase primary winding 18uv, through the a-phase reactor La, the lower capacitor Cd, the switching element S2, and the upper UV-phase primary winding in sequence. During periods t4 and t5, the upper capacitor Cu discharges and the lower capacitor Cd is charged.

[0075] Fig. 6(d) shows the second capacitor current Ic2 (zero-period current) during period t6. During period t6, after the second capacitor current Ic2 in Fig. 6(c) decreases to 0, the flowing direction reverses. That is, the second capacitor current Ic2 flows from the lower UV-phase primary winding, through the switching element S4, the lower capacitor Cd, and the a-phase reactor La in sequence, and returns to the tap of the UV-phase primary winding 18uv. Also, the second capacitor current Ic2 flows from the upper UV-phase primary winding, through the switching element S2, the lower capacitor Cd, and the a-phase reactor La in sequence, and returns to the tap of the UV-phase primary winding 18uv. During period t6, the first capacitor current Ic1 becomes 0, and the lower capacitor Cd changes from the charged state to the discharging state. The voltages across both the upper capacitor Cu and the lower capacitor Cd are determined by the induced electromotive force generated in the a-phase reactor La and the voltage appearing in the UV-phase primary winding 18uv.

[0076] FIG. 7(a) shows the time waveform of the voltage Vuv across both ends of the UV-phase primary winding 18uv. FIG. 7(b) shows the time waveform of the current ILa flowing through the a-phase reactor La. FIG. 7(c) shows the time waveforms of the first capacitor current Ic1 and the second capacitor current Ic2. The horizontal axis represents time, and the vertical axis represents voltage or current. The voltage across both ends of the UV-phase primary winding 18uv, similar to the voltage vta across both ends of the a-phase secondary winding 20a, becomes positive, positive, 0, negative, negative, 0 in sequence during periods t1 to t6. The current ILa flowing through the a-phase reactor La is positive during periods t1 and t2, decreases from positive to 0 during period t3, and then increases from 0 in the negative direction. The current ILa flowing through the a-phase reactor La is negative during periods t4 and t5, increases from negative to 0 during period t6, and then increases from 0 in the positive direction.

[0077] The first capacitor current Ic1 increases with a positive value during periods t1 and t2, decreases from positive to 0 during period t3, and then increases from 0 in the negative direction. The first capacitor current Ic1 increases in the positive direction with a negative value during periods t4 and t5, and becomes 0 during period t6. The second capacitor current Ic2 decreases to 0 with a positive value during periods t1 and t2, and becomes 0 during period t3. The second capacitor current Ic2 increases in the negative direction with a negative value during periods t4 and t5, increases from negative to 0 during period t6, and then increases from 0 in the positive direction. When the first capacitor current Ic1 is positive, the upper capacitor Cu is charged, and when the first capacitor current Ic1 is negative, the upper capacitor Cu discharges. When the second capacitor current Ic2 is positive, the lower capacitor Cd is charged, and when the second capacitor current Ic2 is negative, the lower capacitor Cd discharges.

[0078] In FIG. 8, in the six columns to the right of the columns labeled t1, t2, ··· t6, for periods t1 to t6, the switching states of the upper switching elements S1, S3, and S5 provided in the capacitor-split type power conversion device 10 and the upper switching elements S7, S9, and S11 provided in the power conversion device 40 are shown. The switching states shown in these six columns are the same as those in FIG. 2.

[0079] In the right three columns of FIG. 8, for periods t1 to t6, it shows whether the voltages vLa that appear across both ends of the a-phase reactor La, the voltages vLb that appear across both ends of the b-phase reactor Lb, and the voltages vLc that appear across both ends of the c-phase reactor Lc are positive, 0, or negative. The voltages vLa, vLb, and vLc are the voltages with the tap sides of the UV-phase primary winding 18uv, the VW-phase primary winding 18vw, and the WU-phase primary winding 18wu set to 0 potential, respectively. The voltage vLb lags the voltage vLa by one-third of a cycle. The voltage vLc lags the voltage vLb by one-third of a cycle, and the voltage vLa lags the voltage vLc by one-third of a cycle.

[0080] The voltage vLa becomes 0, 0, negative, 0, 0, positive in order during periods t1 to t6. The voltage vLb becomes 0, positive, 0, 0, negative, 0 in order during periods t1 to t6. The voltage vLc becomes negative, 0, 0, positive, 0, 0 in order during periods t1 to t6.

[0081] In FIGS. 9(a) to 9(d), the simulation results of the power conversion system 100 are shown. FIG. 9(a) shows the time waveform of the current Icc flowing out from the connection point with the upper capacitor Cu and the lower capacitor Cd toward the a-phase reactor La, the b-phase reactor Lb, and the c-phase reactor Lc. FIG. 9(b) shows the time waveforms of the current ILa flowing through the a-phase reactor La, the current ILb flowing through the b-phase reactor Lb, and the current ILc flowing through the c-phase reactor Lc.

[0082] The time waveform of the current ILa is the same as the time waveform shown in FIG. 7(b). The current ILb lags the current ILa by one-third of a cycle. The current ILc lags the current ILb by one-third of a cycle, and the current ILa lags the current ILc by one-third of a cycle.

[0083] The current Icc shown in Fig. 9(a) is the sum of the currents ILa, ILb, and ILc shown in Fig. 9(b). During periods t1 and t4, the currents ILa and ILb decrease, and the current Icc becomes equal to the current ILc. During periods t2 and t5, the currents iLa and ILc decrease, and the current Icc becomes equal to the current ILb. During periods t3 and t6, the currents iLb and ILc decrease, and the current Icc becomes equal to the current ILa.

[0084] Fig. 9(c) shows the time waveforms of the voltage vLa appearing across both ends of the a-phase reactor La, the voltage vLb appearing across both ends of the b-phase reactor Lb, and the voltage vLc appearing across both ends of the c-phase reactor Lc. The voltage vLa is, in order, 0, 0, negative, 0, 0, positive during periods t1 to t6. The voltage vLb lags the voltage vLa by one-third of a cycle. The voltage vLc lags the voltage vLb by one-third of a cycle, and the voltage vLa lags the voltage vLc by one-third of a cycle.

[0085] Fig. 9(d) shows the time waveforms of the voltage vcu across both ends of the upper capacitor Cu and the voltage vcd across both ends of the lower capacitor Cd. The voltages vcu and vcd repeat their increase and decrease in a cycle of one-third of the time from period t1 to t6. When the voltage vcu is above the average value, the voltage vcd is below the average value, and when the voltage vcu is below the average value, the voltage vcd is above the average value.

[0086] As shown in Fig. 9(a), the frequency of the current Icc flowing out from the connection point of the upper capacitor Cu and the lower capacitor Cd is three times the switching frequency of the switching element provided in each switching arm. As shown in Fig. 9(d), the frequencies of the charging current and the discharging current flowing through the upper capacitor Cu and the lower capacitor Cd respectively are three times the switching frequency of the switching element provided in each switching arm. Therefore, capacitors with small capacitances may be used for the upper capacitor Cu and the lower capacitor Cd. Also, the induced electromotive force generated in each phase reactor for charging the upper capacitor Cu and the lower capacitor Cd may be small, and the inductance of each phase reactor may be small, so that each phase reactor can be miniaturized. As a result, the capacitor-split type power conversion device 10 is miniaturized.

[0087] Fig. 10 shows the states of the upper capacitor Cu, the lower capacitor Cd, the current Icc, the current ILa, the current ILb, and the current ILc in each of the periods t1 to t6. The column of "Vcc" associated with the periods t1 to t6 shows the AC component of the voltage vcd across the lower capacitor Cd. In the columns of "Cu" and "Cd", it is shown whether the upper capacitor Cu and the lower capacitor Cd change from the charged state to the discharged state (charge / discharge) or from the discharged state to the charged state (discharge / charge) in each of the periods t1 to t6. In the column of "Icc", it is shown which of the currents ILa, ILb, and ILc the current Icc corresponds to in each of the periods t1 to t6. In the columns of "iLa", "iLb", and "iLc", it is shown whether the currents iLa, iLb, and iLc are positive, decreasing, negative, or increasing, respectively.

[0088] In the above, an embodiment was shown in which the UV-phase primary winding 18uv, the VW-phase primary winding 18vw, and the WU-phase primary winding 18wu are delta-connected to the switching arms 12U, 12V, and 12W. That is, the connection point between the switching elements S1 and S2, the connection point between the switching elements S3 and S4, and the connection point between the switching elements S5 and S6 constitute a delta connection port DP for a multi-phase (three-phase) AC voltage. An embodiment was shown in which the UV-phase primary winding 18uv, the VW-phase primary winding 18vw, and the WU-phase primary winding 18wu are connected to this delta connection port DP. The UV-phase primary winding 18uv, the VW-phase primary winding 18vw, and the WU-phase primary winding 18wu may be star-connected to the switching arms 12U, 12V, and 12W. That is, the connection point of the two switching elements in each of the switching arms 12U, 12V, and 12W may constitute a delta connection port or a star connection port YP.

[0089] FIG. 11 shows the configuration of a power conversion system 102 in which each primary winding of the capacitor-split type power conversion device 11 is star-connected to each switching arm. The connection point between the switching elements S1 and S2, the connection point between the switching elements S3 and S4, and the connection point between the switching elements S5 and S6 constitute a star connection port. One end of the UV-phase primary winding 18uv is connected to the connection point between the switching elements S1 and S2. One end of the VW-phase primary winding 18vw is connected to the connection point between the switching elements S3 and S4. One end of the WU-phase primary winding 18wu is connected to the connection point between the switching elements S5 and S6. The other ends of the UV-phase primary winding 18uv, the VW-phase primary winding 18vw, and the WU-phase primary winding 18wu are commonly connected to the neutral point N. The operation of each switching element of the power conversion system 102 is the same as the operation of each switching element of the power conversion system 100 shown in FIG. 1.

[0090] In FIGS. 1 and 11, an example is shown in which secondary windings 20a, 20b, and 20c are delta-connected to switching arms 22α, 22β, and 22γ. However, the secondary windings 20a, 20b, and 20c may be Y-connected to the switching arms 22α, 22β, and 22γ. That is, the connection points of the two switching elements in each of the switching arms 22α, 22β, and 22γ may form a delta connection port or a Y connection port.

[0091] FIG. 12 shows the configuration of a 1-port / 2-port power conversion system 104 according to the second embodiment of the present invention. The 1-port / 2-port power conversion system 104 includes a capacitor-split type power conversion device 10 and an additional-port type power conversion device 60.

[0092] The additional-port type power conversion device 60 includes switching arms 62A to 62C, secondary windings 28a to 28c, an a-phase reactor LLa, a b-phase reactor LLb, a c-phase reactor LLc, capacitors C3 and C4, positive terminals 66p and 68p, and negative terminals 66n and 68n. The switching arm 62A includes switching elements Sap and San connected in series. The switching arm 62B includes switching elements Sbp and Sbn connected in series, and the switching arm 62C includes switching elements Scp and Scn connected in series.

[0093] The switching arms 62A to 62C and the capacitor C3 are connected in parallel. The upper parallel connection points of the switching arms 62A to 62C and the capacitor C3 are connected to the positive terminal 66p, and the lower parallel connection points of the switching arms 62A to 62C and the capacitor C3 are connected to the negative terminal 66n. A secondary winding 28a is connected between the connection points of the switching elements Sap and San and the connection points of the switching elements Sbp and Sbn. A secondary winding 28b is connected between the connection points of the switching elements Sbp and Sbn and the connection points of the switching elements Scp and Scn. A secondary winding 28c is connected between the connection points of the switching elements Scp and Scn and the connection points of the switching elements Sap and San.

[0094] One end of the a-phase reactor LLa is connected to the tap of the secondary winding 28a. One end of the b-phase reactor LLb and one end of the c-phase reactor LLc are connected to the taps of the secondary winding 28b and the secondary winding 28c, respectively. The other ends of the phase reactors LLa to LLc are connected to the positive terminal 68p. The lower parallel connection point of the switching arms 62A to 62C and the capacitor C3 is connected not only to the negative terminal 66n but also to the negative terminal 68n. A capacitor C4 is connected between the positive terminal 68p and the negative terminal 68n.

[0095] FIG. 12 shows an example in which the secondary windings 28a, 28b, and 28c are delta-connected to the switching arms 62A to 62C, but the secondary windings 28a, 28b, and 28c may be Y-connected to the switching arms 62A to 62C.

[0096] Switching arms 62A, 62B, and 62C each perform the same switching as switching arms 22α, 22β, and 22γ shown in FIG. 1. That is, switching elements Sap and San each perform the same switching as switching elements S7 and S8. Switching elements Sbp and Sbn each perform the same switching as switching elements S9 and S10, and switching elements Scp and Scn each perform the same switching as switching elements S11 and S12.

[0097] The positive terminal 16p and the negative terminal 16n constitute the first port. The positive terminal 66p and the negative terminal 66n constitute the second port, and the positive terminal 68p and the negative terminal 68n constitute the third port. DC power is transmitted between the first port, the second port, and the third port.

[0098] The ratio of the voltage between the positive terminal 68p and the negative terminal 68n to the voltage between the positive terminal 66p and the negative terminal 66n is determined by the ratio of the length of period t1 to the length of period t4, the ratio of the length of period t2 to the length of period t5, and the ratio of the length of period t6 to the length of period t3.

[0099] The power conversion systems 100, 102, and 104 described above may be used in power transmission facilities in V2G, V2H, etc. Also, the power conversion systems 100, 102, and 104 may be mounted on electric vehicles such as hybrid vehicles and electric vehicles.

Description of Reference Numerals

[0100] 10, 11 Capacitor-split type power conversion device, 12 Switching circuit, 12U U-phase switching arm, 12V V-phase switching arm, 12W W-phase switching arm, 14C Capacitor arm, 16p, 30p, 66p, 68p Positive terminal, 16n, 30n, 66n, 68n Negative terminal, 18uv UV-phase primary winding, 18vw VW-phase primary winding, 18wu WU-phase primary winding, 20a a-phase secondary winding, 20b b-phase secondary winding, 20c c-phase secondary winding, 22α α-phase switching arm, 22β β-phase switching arm, 22γ γ-phase switching arm, 28a~28c Secondary windings, 32 Load circuit, 34 Power supply circuit, 40, 60 Power conversion device, 62A~62C Switching arms, S1~S12, Sap, San, Sbp, Sbn, Scp, Scn Switching elements, Cu Upper capacitor, Cd Lower capacitor, La, LLa a-phase reactor, Lb, LLb b-phase reactor, Lc, LLc c-phase reactor, Ta, Tb, Tc Transformers, C0~C4 Capacitors, DP Delta connection port, N Neutral point.

Claims

1. A U-phase switching arm including a first switching element and a second switching element connected in series; A V-phase switching arm including a third switching element and a fourth switching element connected in series; A W-phase switching arm including a fifth switching element and a sixth switching element connected in series; A UV-phase primary winding coupled to an a-phase secondary winding, the UV-phase primary winding being provided between a connection point of the first switching element and the second switching element and a connection point of the third switching element and the fourth switching element; A VW-phase primary winding coupled to a b-phase secondary winding, the VW-phase primary winding being provided between a connection point of the third switching element and the fourth switching element and a connection point of the fifth switching element and the sixth switching element; A WU-phase primary winding coupled to a c-phase secondary winding, the WU-phase primary winding being provided between a connection point of the fifth switching element and the sixth switching element and a connection point of the first switching element and the second switching element; A capacitor arm including a first capacitor and a second capacitor connected in series; An a-phase reactor provided between a tap of the UV-phase primary winding and a connection point of the first capacitor and the second capacitor; A b-phase reactor provided between a tap of the VW-phase primary winding and a connection point of the first capacitor and the second capacitor; A c-phase reactor provided between a tap of the WU-phase primary winding and a connection point of the first capacitor and the second capacitor, and The U-phase switching arm, the V-phase switching arm, the W-phase switching arm, and the capacitor arm are connected in parallel. A power conversion device characterized by this.

2. A U-phase switching arm including a first switching element and a second switching element connected in series; A V-phase switching arm including a third switching element and a fourth switching element connected in series; A W-phase switching arm including a fifth switching element and a sixth switching element connected in series; A U-phase primary winding coupled to an a-phase secondary winding, the U-phase primary winding having one end connected to the connection point of the first switching element and the second switching element, A V-phase primary winding coupled to a b-phase secondary winding, the V-phase primary winding having one end connected to the connection point of the third switching element and the fourth switching element, A W-phase primary winding coupled to a c-phase secondary winding, the W-phase primary winding having one end connected to the connection point of the fifth switching element and the sixth switching element, A capacitor arm comprising a first capacitor and a second capacitor connected in series, An a-phase reactor provided between a tap of the U-phase primary winding and the connection point of the first capacitor and the second capacitor, A b-phase reactor provided between a tap of the V-phase primary winding and the connection point of the first capacitor and the second capacitor, A c-phase reactor provided between a tap of the W-phase primary winding and the connection point of the first capacitor and the second capacitor, The other ends of the U-phase primary winding, the V-phase primary winding, and the W-phase primary winding are commonly connected, A power conversion device, characterized in that the U-phase switching arm, the V-phase switching arm, the W-phase switching arm, and the capacitor arm are connected in parallel.

3. In the power conversion device according to claim 1 or claim 2, The first switching element and the second switching element are alternately turned on and off, The third switching element and the fourth switching element are alternately turned on and off, The fifth switching element and the sixth switching element are alternately turned on and off, The voltage applied to the a-phase secondary winding changes in the order of positive, positive, 0, negative, negative, 0 in one cycle, The voltage applied to the b-phase secondary winding changes in the order of negative, 0, positive, positive, 0, negative in one cycle, In response to the voltage applied to the c-phase secondary winding changing in the order of 0, negative, negative, 0, positive, positive in one cycle, the on / off states of the first switching element, the on / off state of the third switching element, and the on / off state of the fifth switching element change in the order of (on, off, on), (on, off, off), (on, on, off), (off, on, off), (off, on, on), (off, off, on). A power conversion device characterized by this is provided.

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