JP7635085B2 - Non-contact power transmission circuit - Google Patents

Description

The present invention relates to a non-contact power transmission circuit, and in particular to a technology that uses multiple windings for non-contact power transmission.

There has been extensive research into technologies that utilize the output power of batteries or technologies that charge batteries. For example, in recent years, research has been conducted into a technology called V2G (Vehicle to Grid). In V2G, power is supplied from a battery installed in an electric vehicle such as an electric car or hybrid car to a power system such as a commercial power system, and then the power system supplies power to the battery. Another technology related to V2G is called V2H (Vehicle to Home), which supplies power from a battery installed in an electric vehicle to electrical devices used in ordinary homes, offices, etc.

Generally, devices that use batteries use a power conversion device that adjusts the power output from the battery and outputs it to the device to which the power is supplied, or adjusts power supplied from an external source and supplies it to the battery. Some power conversion devices use multiple switching circuits and a transformer that couples the switching circuits to match the voltage applied to the external device with the output voltage of the battery. In some cases, the transformer is used in a design that insulates the part operated by the user from the battery. In some devices, a device with a primary winding of a transformer and a device with a secondary winding of the transformer are separately configured, and the device on the primary winding side and the device on the secondary winding side are detachable by a connector.

The following Patent Documents 1 to 3 and Non-Patent Documents 1 to 3 describe power conversion devices that couple two switching circuits with a transformer. In the power conversion devices described in Patent Documents 1 and 2, a connector having a primary winding is coupled with a connector having a secondary winding to form a transformer. The power conversion devices described in Patent Document 3 and Non-Patent Documents 1 to 3 include a transformer and a boost inductor, and transmit power with boost from the primary winding side to the secondary winding side of the transformer.

Patent Document 4 describes, as a technology related to the present invention, a magnetic component in which two reactors included in different current paths, whose currents should be controlled independently of each other, are integrally configured. Non-Patent Document 4 describes switching the number of phases of a multi-phase converter depending on the power transmission efficiency. Non-Patent Document 5 describes improving the power transmission efficiency of two isolated converters by switching the number of operating isolated converters.

U.S. Pat. No. 5,341,083 US Patent Publication No. 2017/179765 U.S. Pat. No. 1,026,3456 JP 2013-198246 A

Hui Li, Fang Zheng Peng and J. S. Lawler, "A natural ZVS medium-power bidirectional DC-DC converter with minimum number of devices," in IEEE Transactions on Industry Applications, vol. 39, no. 2, pp. 525-535, March-April 2003, doi: 10.1109/TIA.2003.808965. R. N. M. de Oliveira, L. C. S. Mazza, D. S. Oliveira and H. M. Oliveira Filho, "A three-port three-phase isolated DC-DC converter feasible to PV connection on a DC distribution system," 2017 Brazilian Power Electronics Conference (COBEP), Juiz de Fora, 2017, pp. 1-6, doi: 10.1109/COBEP.2017.8257272. Wang, Zhan; Li, Hui, “Integrated three-port bidirectional DC-DC converter for renewable energy sources”, Patent No. 10263456 P. Zumel, C. Fernandez, A. de Castro and O. Garcia, "Efficiency improvement in multiphase converter by changing dynamically the number of phases," 2006 37th IEEE Power Electronics Specialists Conference, Jeju, 2006, pp. 1-6, doi: 10.1109/pesc.2006.1712202. M. Rolak, C. Sobol, M. Malinowski and S. Stynski, "Efficiency Optimization of Two Dual Active Bridge Converters Operating in Parallel," in IEEE Transactions on Power Electronics, vol. 35, no. 6, pp. 6523-6532, June 2020, doi: 10.1109/TPEL.2019.2951833.

As a power conversion device using a transformer, a device that transmits multiple phases of power to an external device using a multiple phase transformer has been proposed. Depending on the amount of power transmitted to the external device, the power transmission efficiency may be improved compared to when a single phase transformer is used. Also, in order to reduce power loss in the circuits and transformers within the power conversion device, various structures have been devised for the windings of each phase.

However, if the winding structure is designed with a focus only on power loss, bias in the magnetic characteristics of the windings of multiple phases can occur. This can result in, for example, a need to enlarge the core to avoid magnetic saturation of the winding core of a particular phase, resulting in a larger transformer.

The object of the present invention is to make the magnetic characteristics of multiple windings uniform in a non-contact power transmission circuit having multiple windings.

The present invention comprises a switching circuit including an A-phase winding, a B-phase winding, and a C-phase winding, the A-phase winding, the B-phase winding, and the C-phase winding forming an inter-phase non-interference winding structure, and the switching circuit switches the A-phase winding, the B-phase winding, and the C-phase winding so that the phase of the terminal voltage of the A-phase winding leads the phase of the terminal voltage of the C-phase winding in a range of more than 60° and less than 120°, and the phase of the terminal voltage of the B-phase winding lags the phase of the terminal voltage of the C-phase winding in a range of more than 60° and less than 120°. The voltages applied to the B-phase winding and the C-phase winding are switched, or the voltages applied to the A-phase winding, the B-phase winding, and the C-phase winding are switched so that the phase of the terminal voltage of the A-phase winding lags the phase of the terminal voltage of the C-phase winding in a range of more than 60° and less than 120°, and the phase of the terminal voltage of the B-phase winding leads the phase of the terminal voltage of the C-phase winding in a range of more than 60° and less than 120°.

Desirably, the switching circuit switches the voltages applied to the A-phase winding, the B-phase winding, and the C-phase winding, respectively, so that the phase of the terminal voltage of the A-phase winding leads the phase of the terminal voltage of the C-phase winding by 90° and the phase of the terminal voltage of the B-phase winding lags the phase of the terminal voltage of the C-phase winding by 90°, or switches the voltages applied to the A-phase winding, the B-phase winding, and the C-phase winding, respectively, so that the phase of the terminal voltage of the A-phase winding lags the phase of the terminal voltage of the C-phase winding by 90° and the phase of the terminal voltage of the B-phase winding leads the phase of the terminal voltage of the C-phase winding by 90°.

The present invention also relates to an A-phase switching arm, a B-phase switching arm, and a C-phase switching arm that are connected in parallel, each of which includes an upper switching element and a lower switching element that are commonly connected at one end, and an A-phase winding provided for the A-phase switching arm, the A-phase winding having one end connected to a connection point of the upper switching element and the lower switching element included in the A-phase switching arm, and a B-phase winding provided for the B-phase switching arm. The inverter comprises a B-phase winding having one end connected to a connection point between the upper switching element and the lower switching element included in the B-phase switching arm, and a C-phase winding provided for the C-phase switching arm, having one end connected to a connection point between the upper switching element and the lower switching element included in the C-phase switching arm, wherein the A-phase winding, the B-phase winding, and the C-phase winding form an inter-phase non-interference winding structure, and a common power source or load is connected to the other end of each of the A-phase winding, the B-phase winding, and the C-phase winding.

Desirably, the switching phase of the A-phase switching arm is advanced relative to the switching phase of the C-phase switching arm by a range of more than 60° and less than 120°, and the switching phase of the B-phase switching arm is delayed relative to the switching phase of the C-phase switching arm by a range of more than 60° and less than 120°, or the switching phase of the A-phase switching arm is delayed relative to the switching phase of the C-phase switching arm by a range of more than 60° and less than 120°, and the switching phase of the B-phase switching arm is advanced relative to the switching phase of the C-phase switching arm by a range of more than 60° and less than 120°.

Desirably, the switching phase of the A-phase switching arm leads the switching phase of the C-phase switching arm by 90° and the switching phase of the B-phase switching arm lags the switching phase of the C-phase switching arm by 90°, or the switching phase of the A-phase switching arm lags the switching phase of the C-phase switching arm by 90° and the switching phase of the B-phase switching arm leads the switching phase of the C-phase switching arm by 90°.

Desirably, the motor includes a first core and a second core that pass through the forward and reverse wound loops of the A-phase winding, respectively, and a third core and a fourth core that pass through the forward and reverse wound loops of the B-phase winding, respectively, and the first core and the second core that pass through the A-phase winding pass through the forward wound loop of the C-phase winding, and the third core and the fourth core that pass through the B-phase winding pass through the reverse wound loop of the C-phase winding.

Preferably, each of the first core to the fourth core is formed in a rod shape, and each of the first core to the fourth core has a common core commonly connected to one end thereof.

The present invention also provides a device that includes a plurality of switching arms connected in parallel, each of which includes an upper switching element and a lower switching element, one end of which is commonly connected, a winding provided for each of the switching arms, one end of which is connected to a connection point between the upper switching element and the lower switching element, and a control unit that controls each of the switching arms, the other ends of the windings are commonly connected, and a common power source or load is connected to the other ends of the windings, each of the windings is coupled to a corresponding one of a plurality of external windings of an external switching circuit, the plurality of windings provided corresponding to the plurality of switching arms form a phase-to-phase non-interference winding structure, and the control unit causes a number of the switching arms, among the plurality of the switching arms, that correspond to a command value for the transmission power to the switching circuit, to perform switching.

According to the present invention, it is possible to uniformize the magnetic properties of multiple windings in a non-contact power transmission circuit having multiple windings.

1 is a diagram showing a configuration of a power conversion system according to a first embodiment. FIG. 2 is a diagram illustrating a configuration example of a three-phase interphase decoupling transformer. FIG. 2 is a diagram illustrating a configuration example of a three-phase interphase decoupling transformer. 2 is a diagram showing magnetic fluxes Φ1 to Φ4 passing through a first rectangular prism core to a fourth rectangular prism core, respectively. 11A and 11B are diagrams showing the time waveforms of each phase voltage, the time waveforms of each phase magnetic flux, and the time waveforms of magnetic fluxes Φ1 to Φ4 passing through a first to fourth rectangular prism cores, respectively. 11A and 11B are diagrams showing the time waveforms of each phase voltage, the time waveforms of each phase magnetic flux, and the time waveforms of magnetic fluxes Φ1 to Φ4 passing through a first to fourth rectangular prism cores, respectively. 11A and 11B are diagrams showing the time waveforms of each phase voltage, the time waveforms of each phase magnetic flux, and the time waveforms of magnetic fluxes Φ1 to Φ4 passing through a first to fourth rectangular prism cores, respectively. 11A and 11B are diagrams showing the time waveforms of each phase voltage, the time waveforms of each phase magnetic flux, and the time waveforms of magnetic fluxes Φ1 to Φ4 passing through a first to fourth rectangular prism cores, respectively. FIG. 13 is a diagram showing the relationship between maximum magnetic flux and inter-phase phase difference. 1 is a diagram showing a configuration of a power conversion system according to a first application embodiment. FIG. 11 is a diagram showing a configuration of a power conversion system according to a second application embodiment. FIG. 13 is a diagram showing a configuration of a power conversion system according to a third application embodiment. FIG. 11 is a diagram showing a configuration of a power conversion system according to a second embodiment. FIG. 11 is a diagram showing the relationship between transmission power and power transmission efficiency.

Each embodiment of the present invention will be described with reference to each figure. Identical items shown in multiple drawings will be given the same reference numerals and their description will be omitted. The terms up, down, left, right, and so on used in this specification indicate directions in the drawings. These directional terms are used for the convenience of explanation and do not limit the orientation of each component when it is placed.

Figure 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 first switching circuit 10 and a second switching circuit 20 that are magnetically coupled. Power is transmitted in both directions between a first DC power source 30 connected to the first switching circuit 10 and a second DC power source 36 connected to the second switching circuit 20.

The first DC power source 30 may include a commercial power source system 32 (power source power system) provided by a power company and an AC/DC converter 34. The AC/DC converter 34 converts the AC voltage supplied from the commercial power source system 32 into a DC voltage and outputs the DC voltage to the first switching circuit 10. The first DC power source 30 may also be a circuit including a secondary battery. The second DC power source 36 may also be a circuit including a secondary battery, or may be an AC/DC converter connected to the commercial power source system. When the first DC power source 30 includes a secondary battery and the secondary battery is charged, the first DC power source 30 operates as a load. Similarly, when the second DC power source 36 includes a secondary battery and the secondary battery is charged, the second DC power source 36 operates as a load.

As described below, the combined circuit of the AC/DC converter 34 and the first switching circuit 10, and the second switching circuit 20 may each be used as a contactless connector circuit (contactless power transmission circuit). That is, the AC/DC converter 34 and the first switching circuit 10 may be housed in a first housing, and the second switching circuit 20 may be housed in a second housing that is detachable from the first housing, thereby forming a primary side contactless connector and a secondary side contactless connector.

The first switching circuit 10 includes an upper capacitor C1, a lower capacitor C2, a U-phase switching arm α1, a V-phase switching arm β1, a W-phase switching arm γ1, a U-phase primary winding 14u, a V-phase primary winding 14v, a W-phase primary winding 14w, a positive terminal 12p, and a negative terminal 12n. Each switching arm includes an upper switching element SH and a lower switching element SL connected in series. The upper capacitor C1 and the lower capacitor C2 are connected in series to form a capacitor arm CA1. The connection point between the upper capacitor C1 and the lower capacitor C2 is connected to the positive terminal 12p, and the lower end of the lower capacitor C2 is connected to the negative terminal 12n. The AC/DC converter 34 applies a DC voltage to the positive terminal 12p and the negative terminal 12n.

The capacitor arm CA1, U-phase switching arm α1, V-phase switching arm β1, and W-phase switching arm γ1 are connected in parallel. One end of the U-phase primary winding 14u is connected to the connection end between the upper switching element SH and the lower switching element SL in the U-phase switching arm α1. One end of the V-phase primary winding 14v is connected to the connection end between the upper switching element SH and the lower switching element SL in the V-phase switching arm β1. One end of the W-phase primary winding 14w is connected to the connection end between the upper switching element SH and the lower switching element SL in the W-phase switching arm γ1.

The other ends of the U-phase primary winding 14u, the V-phase primary winding 14v, and the W-phase primary winding 14w are commonly connected. The common connection point of the U-phase primary winding 14u, the V-phase primary winding 14v, and the W-phase primary winding 14w is connected to the connection point of the upper capacitor C1 and the lower capacitor C2.

Each switching element may be an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). When an IGBT is used as a switching element, two switching elements connected in series means that the emitter electrode of one element is connected to the collector electrode of the other element. When a MOSFET is used as a switching element, two switching elements connected in series means that the source electrode of one element is connected to the drain electrode of the other element.

When an IGBT is used as the switching element, the switching element has a diode with an anode electrode connected to the emitter electrode of the IGBT and a cathode electrode connected to the collector electrode. When a MOSFET is used as the switching element, the switching element has a diode with an anode electrode connected to the source electrode of the MOSFET and a cathode electrode connected to the drain electrode.

The second switching circuit 20 includes a capacitor arm CA2, a U-phase switching arm α2, a V-phase switching arm β2, a W-phase switching arm γ2, a U-phase secondary winding 24u, a V-phase secondary winding 24v, a W-phase secondary winding 24w, a positive terminal 22p, and a negative terminal 22n. The capacitor arm CA2 includes an upper capacitor C1 and a lower capacitor C2 connected in series. Each switching arm includes an upper switching element SH and a lower switching element SL connected in series.

The second switching circuit 20 has a configuration similar to that of the first switching circuit 10. The capacitor arm CA2, the U-phase switching arm α2, the V-phase switching arm β2, and the W-phase switching arm γ2 correspond to the capacitor arm CA1, the U-phase switching arm α1, the V-phase switching arm β1, and the W-phase switching arm γ1, respectively. The U-phase secondary winding 24u, the V-phase secondary winding 24v, and the W-phase secondary winding 24w correspond to the U-phase primary winding 14u, the V-phase primary winding 14v, and the W-phase primary winding 14w, respectively. The positive terminal 22p and the negative terminal 22n correspond to the positive terminal 12p and the negative terminal 12n, respectively.

The U-phase primary winding 14u, the V-phase primary winding 14v, and the W-phase primary winding 14w are coupled to the U-phase secondary winding 24u, the V-phase secondary winding 24v, and the W-phase secondary winding 24w, respectively, and each primary winding and each secondary winding constitutes a three-phase transformer 38.

The upper switching element SH and the lower switching element SL of each switching arm of the first switching circuit 10 and the second switching circuit 20 are alternately turned on and off. That is, as the upper switching element SH switches from off to on, the lower switching element SL switches from on to off, and as the upper switching element SH switches from on to off, the lower switching element SL switches from off to on.

The components belonging to the U-phase, V-phase, and W-phase operate in the same way, so here we will explain the operation of the components belonging to the U-phase. The voltage applied to the U-phase primary winding 14u is switched by switching the U-phase switching arm α1. The voltage applied to the U-phase secondary winding 24u is switched by switching the U-phase switching arm α2. As a result, currents flow in the U-phase primary winding 14u and the U-phase secondary winding 24u according to their respective self-inductances and their mutual inductances.

Depending on the relationship between the magnitude and phase of the voltage appearing in the U-phase primary winding 14u and the voltage appearing in the U-phase secondary winding 24u, power is transmitted from the U-phase primary winding 14u to the U-phase secondary winding 24u, or power is transmitted from the U-phase secondary winding 24u to the U-phase primary winding 14u. In addition, depending on the duty ratio of the U-phase switching arm α1 and the duty ratio of the U-phase switching arm α2, the voltage appearing in the U-phase primary winding 14u and the U-phase secondary winding 24u changes, and the power exchanged between the U-phase primary winding 14u and the U-phase secondary winding 24u changes. Here, the duty ratio of each switching arm is defined as the ratio of the on time to the switching period of the upper switching element SH.

The power _P21 transmitted from the first switching circuit 10 to the second switching circuit 20 is determined as follows. That is, the power _P21 is determined by the duty ratio _D1 of the U-phase switching arm α1, the duty ratio _D2 of the U-phase switching arm α2, and the switching phase difference δ. Here, the switching phase difference δ refers to the delay in the switching phase of the U-phase switching arm α2 relative to the U-phase switching arm α1. There are numerical ranges for the duty ratios _D1 , _D2 and the switching phase difference δ such that the power _P21 increases as the switching phase difference δ increases in the positive direction.

Equation 1 shows the power P ₂₁ transferred from the first switching circuit 10 to the second switching circuit 20 .

However, equation 1 indicates an equation assuming that the switching phase difference δ≧π|D ₁ -D ₂ | holds. The primary side DC voltage Vin is the voltage between the positive terminal 12p and the negative terminal 12n of the first switching circuit 10, and the secondary side DC voltage Vout is the voltage between the positive terminal 22p and the negative terminal 22n of the second switching circuit 20. Furthermore, ω is the angular frequency of switching, and k is the coupling coefficient between the U-phase primary winding 14u and the U-phase secondary winding 24u.

By delaying the switching phase of the second switching circuit 20 relative to the switching phase of the first switching circuit 10, power can be transmitted from the first DC power source 30 to the second DC power source 36. Also, by delaying the switching phase of the first switching circuit 10 relative to the switching phase of the second switching circuit 20, power can be transmitted from the second DC power source 36 to the first DC power source 30.

The combined circuit of the AC/DC converter 34 and the first switching circuit 10, and the second switching circuit 20 may each be used as a contactless connector circuit (contactless power transmission circuit). That is, the AC/DC converter 34 and the first switching circuit 10 may be housed in a first housing, and the second switching circuit 20 may be housed in a second housing that is detachable from the first housing, thereby forming a primary side contactless connector and a secondary side contactless connector.

Each primary winding included in the contactless connector on the primary side is coupled to each secondary winding (external winding) of the external switching circuit, with the contactless connector circuit on the secondary side serving as the external switching circuit. Each secondary winding included in the contactless connector on the secondary side is coupled to each primary winding (external winding) of the external switching circuit, with the contactless connector circuit on the primary side serving as the external switching circuit.

In this case, the AC/DC converter 34 in the first DC power supply 30 may be housed in a housing separate from the first housing, and a cable drawn from the first DC power supply 30 may be connected to the first switching circuit 10 in the first housing. The second DC power supply 36 may be housed in a housing separate from the second housing, and a cable drawn from the second DC power supply 36 may be connected to the second switching circuit 20 in the second housing. By bringing the first housing and the second housing close to each other or isolating them, the primary winding and secondary winding of each phase are brought close to each other or isolated.

The primary windings of each phase may be housed in a first housing, and the other components of the first switching circuit 10 may be housed in a separate housing. Similarly, the secondary windings of each phase may be housed in a second housing, and the other components of the second switching circuit 20 may be housed in a separate housing.

The three-phase transformer 38 may be an interphase decoupling transformer 38N with small interphase coupling. FIG. 2 shows an example of the configuration of a three-phase interphase decoupling transformer 38N. The interphase decoupling transformer 38N has a primary winding structure 16 and a secondary winding structure 26 as interphase decoupling winding structures on the primary and secondary sides. The primary winding structure 16 has a primary core 40-1, a U-phase primary winding 14u, a V-phase primary winding 14v, and a W-phase primary winding 14w. The primary core 40-1 has a horizontal core 46 and a first vertical core 41 to a fourth vertical core 44. The horizontal core 46 and the first vertical core 41 to the fourth vertical core 44 are formed in a columnar shape such as a rectangular column shape or a cylindrical shape.

The horizontal core 46 extends horizontally. The first vertical core 41 extends upward from the left end of the horizontal core 46. The second vertical core 42 extends upward from the horizontal core 46 to the right of the first vertical core 41, with a predetermined distance between them. The third vertical core 43 extends upward from the horizontal core 46 to the right of the second vertical core 42, with a predetermined distance between them. The fourth vertical core 44 extends upward from the right end of the horizontal core 46 to the right of the third vertical core 43, with a predetermined distance between them.

The secondary winding structure 26 has a configuration similar to that of the primary winding structure 16, and includes a secondary core 40-2, a U-phase secondary winding 24u, a V-phase secondary winding 24v, and a W-phase secondary winding 24w. However, in the example shown in FIG. 2, the winding direction of each winding in the secondary winding structure 26 is the opposite direction to that of the primary winding structure 16 when the primary core 40-1 and the secondary core 40-2 are in the same position and the conductor is traced from the reference end. The reference end of each winding is defined as follows. That is, when the current flowing in from one end of the primary winding increases and an induced electromotive force is generated in the secondary winding, the one end of the secondary winding on the side where the polarity of the induced electromotive force is positive is the reference end of the secondary winding, and the one end of the primary winding where the current flowing in has increased is the reference end of the primary winding.

The secondary winding structure 26 is arranged such that the tip faces of the first vertical core 41 to the fourth vertical core 44 of the secondary core 40-2 face the tip faces of the first vertical core 41 to the fourth vertical core 44 of the primary core 40-1, respectively, across a predetermined gap length. A jth gap Gj is formed between the jth vertical core of the primary core 40-1 and the jth vertical core of the secondary core 40-2, where j is an integer between 1 and 4.

The primary winding structure 16 and the secondary winding structure 26 have the same configuration, except for the winding direction when viewed with the core in the same position. Therefore, this specification mainly describes the operation of the primary winding structure 16, and the description of the operation of the secondary winding structure 26 is simplified or omitted.

The U-phase primary winding 14u, the V-phase primary winding 14v, and the W-phase primary winding 14w constitute a three-phase primary winding as a three-phase transformer winding. The U-phase secondary winding 24u, the V-phase secondary winding 24v, and the W-phase secondary winding 24w constitute a three-phase secondary winding as a three-phase transformer winding. Of the two ends of each of the U-phase primary winding 14u, the V-phase primary winding 14v, and the W-phase primary winding 14w, a black dot is marked on the side that is designated as the reference end. Similarly, of the two ends of each of the U-phase secondary winding 24u, the V-phase secondary winding 24v, and the W-phase secondary winding 24w, a black dot is also marked on the side that is designated as the reference end.

The wire constituting the U-phase primary winding 14u winds clockwise around the second vertical core 42, then winds counterclockwise around the first vertical core 41. The wire constituting the V-phase primary winding 14v winds clockwise around the fourth vertical core 44, then winds counterclockwise around the third vertical core 43. The wire constituting the W-phase primary winding 14w winds clockwise around the third vertical core 43 and the fourth vertical core 44, then winds counterclockwise around the second vertical core 42 and the first vertical core 41.

In this way, the conductors constituting the U-phase primary winding 14u, the V-phase primary winding 14v, and the W-phase primary winding 14w are wound around the vertical core in a figure of eight. Each conductor may wind around one of the two loops forming the figure of eight one or more times, and then wind around the other loop one or more times. Each conductor may also wind around the vertical core such that the winding process of winding one figure of eight once, and then winding the next figure of eight once, is repeated multiple times.

When a current flows through the U-phase primary winding 14u, a U-phase magnetic flux Φu is generated that passes through the first vertical core 41 of the primary core 40-1, the first gap G1, the first vertical core 41 of the secondary core 40-2, the horizontal core 46 of the secondary core 40-2, the second vertical core 42 of the secondary core 40-2, the second gap G2, the second vertical core 42 of the primary core 40-1, and the horizontal core 46 of the primary core 40-1. This U-phase magnetic flux Φu generates an induced electromotive force in the U-phase secondary winding 24u.

When a current flows through the V-phase primary winding 14v, a V-phase magnetic flux Φv is generated that passes through the third vertical core 43 of the primary core 40-1, the third gap G3, the third vertical core 43 of the secondary core 40-2, the horizontal core 46 of the secondary core 40-2, the fourth vertical core 44 of the secondary core 40-2, the fourth gap G4, the fourth vertical core 44 of the primary core 40-1, and the horizontal core 46 of the primary core 40-1. This V-phase magnetic flux Φv generates an induced electromotive force in the V-phase secondary winding 24v.

When a current flows through the W-phase primary winding 14w, a magnetic flux Φw1 is generated that passes through the first vertical core 41 of the primary core 40-1, the first gap G1, the first vertical core 41 of the secondary core 40-2, the horizontal core 46 of the secondary core 40-2, the fourth vertical core 44 of the secondary core 40-2, the fourth gap G4, the fourth vertical core 44 of the primary core 40-1, and the horizontal core 46 of the primary core 40-1. In addition, a magnetic flux Φw2 is generated that passes through the second vertical core 42 of the primary core 40-1, the second gap G2, the second vertical core 42 of the secondary core 40-2, the horizontal core 46 of the secondary core 40-2, the third vertical core 43 of the secondary core 40-2, the third gap G3, the third vertical core 43 of the primary core 40-1, and the horizontal core 46 of the primary core 40-1. These magnetic fluxes Φw1 and Φw2 generate an induced electromotive force in the W-phase secondary winding 24w.

More generally, if the U-phase primary winding 14u is an A-phase winding or a B-phase winding, the V-phase primary winding 14v is a B-phase winding or an A-phase winding, and the W-phase primary winding 14w is a C-phase winding, the primary winding structure 16 constituting the interphase non-interference transformer 38N has the following interphase non-interference winding structure. That is, each of the A-phase winding, the B-phase winding, and the C-phase winding includes a forward winding loop and a reverse winding loop. The forward winding loop of the C-phase winding surrounds the magnetic flux generated by the forward winding loop and the reverse winding loop of the A-phase winding, and the reverse winding loop of the C-phase winding surrounds the magnetic flux generated by the forward winding loop and the reverse winding loop of the B-phase winding.

The terms "forward wound loop" and "reverse wound loop" herein mean that the winding direction of one loop is opposite to the winding direction of the other loop, and refer to two loops with relatively opposite winding directions. The terms "forward wound loop" and "reverse wound loop" do not necessarily mean absolute winding directions based on some winding direction.

The non-interference winding structure also includes a first core and a second core that pass through the forward and reverse wound loops of the A-phase winding, respectively, and a third core and a fourth core that pass through the forward and reverse wound loops of the B-phase winding, respectively. The first core and the second core that pass through the A-phase winding pass through the forward wound loop of the C-phase winding, and the third core and the fourth core that pass through the B-phase winding pass through the reverse wound loop of the C-phase winding.

In the interphase decoupling transformer 38N, if the U-phase primary winding 14u, the V-phase primary winding 14v, and the W-phase primary winding 14w are respectively the A-phase winding, the B-phase winding, and the C-phase winding, the first vertical core 41 to the fourth vertical core 44 correspond to the first core to the fourth core, respectively. Each of the first vertical core 41 to the fourth vertical core 44 (first core to fourth core) is formed in a columnar (rod-like) shape, and one end of each of the first vertical core 41 to the fourth vertical core 44 is commonly connected to a horizontal core 46 (common core).

The first switching circuit 10 and the second switching circuit 20 include an A-phase switching arm, a B-phase switching arm, and a C-phase switching arm connected in parallel, an A-phase winding having one end connected to a connection point of the upper switching element SH and the lower switching element SL included in the A-phase switching arm, a B-phase winding having one end connected to a connection point of the upper switching element SH and the lower switching element SL included in the B-phase switching arm, and a C-phase winding having one end connected to a connection point of the upper switching element SH and the lower switching element SL included in the A-phase switching arm. The A-phase winding, the B-phase winding, and the C-phase winding form a non-interference winding structure between phases, and a common first DC power source 30 or a second DC power source 36 (power source or load) is connected to the other end of each of the A-phase winding, the B-phase winding, and the C-phase winding.

With this configuration, the magnetic flux emitted from one of the two loops forming a figure of eight in one winding does not pass through (does not intersect with) either of the two loops forming a figure of eight in the other winding, or it intersects with the two loops forming a figure of eight in the other winding. When the magnetic flux emitted from one of the two loops forming a figure of eight intersects with the two loops forming a figure of eight in the other winding, an induced electromotive force of opposite polarity is generated in the two loops of the other winding. Therefore, the induced electromotive force generated between the terminals of the other winding is suppressed.

The degree to which the effect of the magnetic flux emitted from one winding loop generating an induced electromotive force of opposite polarity in two loops of the other winding can be adjusted by the number of turns of each winding, the cross-sectional area of each core, the length of each gap, etc.

When there is coupling between phases in a multi-phase transformer, the current flowing through each winding and the switching circuit connected to each winding may differ from the ideal current, resulting in large losses in the windings and switching circuits. By using the phase-to-phase non-interference transformer 38N in the power conversion system 100, the phenomenon in which the current flowing through each winding differs from the ideal current is suppressed, and power losses in the first switching circuit 10 and the second switching circuit 20 are reduced.

Figure 3 shows a schematic diagram of an example of the configuration of an interphase decoupling transformer. The interphase decoupling transformer 38A is a modified version of the primary core 40-1 and secondary core 40-2 of the interphase decoupling transformer 38N in Figure 2. The interphase decoupling transformer 38A has a primary winding structure 16 and a secondary winding structure 26. The primary winding structure 16 has a primary core 60-1, a U-phase primary winding 14u, a V-phase primary winding 14v, and a W-phase primary winding 14w, and the secondary winding structure 26 has a secondary core 60-2, a U-phase secondary winding 24u, a V-phase secondary winding 24v, and a W-phase secondary winding 24w. The primary core 60-1 is composed of a rectangular plate-shaped core 66 and a first square prism core 61 to a fourth square prism core 64 protruding from the four corners of the plate-shaped core 66 toward the front side. The plate-shaped core 66 corresponds to the horizontal core 46 of the interphase decoupling transformer 38N, and the first rectangular prism core 61 to the fourth rectangular prism core 64 correspond to the first vertical core 41 to the fourth vertical core 44 of the interphase decoupling transformer 38N.

One of the two loops in the figure of eight formed by the U-phase primary winding 14u goes around the first rectangular prism core 61, and the other goes around the second rectangular prism core 62. One of the two loops in the figure of eight formed by the V-phase primary winding 14v goes around the third rectangular prism core 63, and the other goes around the fourth rectangular prism core 64. One of the two loops in the figure of eight formed by the W-phase primary winding 14w goes around the first rectangular prism core 61 and the second rectangular prism core 62, and the other goes around the third rectangular prism core 63 and the fourth rectangular prism core 64.

The primary core 60-1 and secondary core 60-2 have a symmetrical structure with respect to the plane between them. The secondary core 60-2 is composed of a rectangular plate-like core 66 and a first quadrangular prism core 61 to a fourth quadrangular prism core 64 that protrude from the four corners of the plate-like core 66 toward the rear side. The tip faces of the first quadrangular prism core 61 to the fourth quadrangular prism core 64 in the secondary core 60-2 face the tip faces of the first quadrangular prism core 61 to the fourth quadrangular prism core 64 in the primary core 60-1, respectively, across a predetermined gap length.

Figure 4 shows magnetic fluxes Φ1 to Φ4 passing through the first to fourth rectangular prism cores 61 to 64 in the primary winding structure 16. The polarity of the magnetic fluxes Φ1 to Φ4 is positive when the magnetic flux is directed from the back to the front at a given time. There is the following relationship between the magnetic fluxes Φ1 to Φ4 and the U-phase magnetic flux Φu, V-phase magnetic flux Φv, and W-phase magnetic flux Φw. Here, the U-phase magnetic flux Φu, V-phase magnetic flux Φv, and W-phase magnetic flux Φw are the magnetic fluxes generated by the U-phase primary winding 14u, V-phase primary winding 14v, and W-phase primary winding 14w, respectively.

(Equation 2)
Φ1 = Φw + Φu
Φ2 = Φw - Φu
Φ3 = -Φw -Φv
Φ4 = -Φw + Φv

In this embodiment, the switching phases of the U-phase switching arms α1 and α2 may lead the switching phases of the W-phase switching arms γ1 and γ2 by more than 60° and less than 120°, respectively. The switching phases of the V-phase switching arms β1 and β2 may lag the switching phases of the W-phase switching arms γ1 and γ2 by more than 60° and less than 120°, respectively.

Preferably, the switching phases of the U-phase switching arms α1 and α2 may lead the switching phases of the W-phase switching arms γ1 and γ2 by 90°, respectively. The switching phases of the V-phase switching arms β1 and β2 may lag the switching phases of the W-phase switching arms γ1 and γ2 by 90°, respectively.

In addition, in this embodiment, the switching phases of the U-phase switching arms α1 and α2 may lag behind the switching phases of the W-phase switching arms γ1 and γ2, respectively, in a range of more than 60° and less than 120°. The switching phases of the V-phase switching arms β1 and β2 may lead behind the switching phases of the W-phase switching arms γ1 and γ2, respectively, in a range of more than 60° and less than 120°.

Preferably, the switching phases of the U-phase switching arms α1 and α2 may lag the switching phases of the W-phase switching arms γ1 and γ2 by 90°, respectively. The switching phases of the V-phase switching arms β1 and β2 may lead the switching phases of the W-phase switching arms γ1 and γ2 by 90°, respectively.

Figure 5 (a) shows the outline of the time waveforms of the U-phase voltage Vu, the V-phase voltage Vv, and the W-phase voltage Vw. Here, the U-phase voltage Vu, the V-phase voltage Vv, and the W-phase voltage Vw are the terminal voltages of the U-phase primary winding 14u, the V-phase primary winding 14v, and the W-phase primary winding 14w, respectively. The terminal voltages of the U-phase primary winding 14u, the V-phase primary winding 14v, and the W-phase primary winding 14w are the voltages of the switching element connection points of the U-phase switching arm α1, the V-phase switching arm β1, and the W-phase switching arm γ1, respectively. Here, the switching element connection point refers to the connection point between the upper switching element SH and the lower switching element SL, and the voltage of the switching element connection point of each switching arm is based on the potential of the connection point between the upper capacitor C1 and the lower capacitor C2.

In the example shown in FIG. 5(a), the time waveform of the voltage of each phase is a square wave, and the U-phase voltage Vu lags the W-phase voltage Vw by 120°. The V-phase voltage Vv leads the W-phase voltage Vw by 120°.

Figure 5(b) shows the outline of the time waveforms of the U-phase magnetic flux Φu, the V-phase magnetic flux Φv, and the W-phase magnetic flux Φw. The time waveforms of the U-phase magnetic flux Φu, the V-phase magnetic flux Φv, and the W-phase magnetic flux Φw are approximate to the time waveforms obtained by integrating the U-phase voltage Vu, the V-phase voltage Vv, and the W-phase voltage Vw, respectively.

Figure 5 (c) shows the outline of the time waveforms of the magnetic fluxes Φ1 to Φ4 passing through the first rectangular prism core 61 to the fourth rectangular prism core 64, respectively. The amplitudes of the magnetic fluxes Φ2 and Φ4 (the sum of the positive and negative crest values) are greater than the amplitudes of the magnetic fluxes Φ1 and Φ3.

Here, the case is shown in which the U-phase voltage Vu lags the W-phase voltage Vw by 120° and the V-phase voltage Vv leads the W-phase voltage Vw by 120°. However, even if the U-phase voltage Vu leads the W-phase voltage Vw by 120° and the V-phase voltage Vv lags the W-phase voltage Vw by 120°, the amplitude of the magnetic fluxes Φ2 and Φ4 will be greater than the amplitude of the magnetic fluxes Φ1 and Φ3.

Figure 6(a) shows the outline of the time waveforms of the U-phase voltage Vu, V-phase voltage Vv, and W-phase voltage Vw when the U-phase voltage Vu leads the W-phase voltage Vw by 90° and the V-phase voltage Vv lags the W-phase voltage Vw by 90°. Figure 6(b) shows the outline of the time waveforms of the U-phase magnetic flux Φu, V-phase magnetic flux Φv, and W-phase magnetic flux Φw. Figure 6(c) shows the outline of the time waveforms of the magnetic fluxes Φ1 to Φ4 passing through the first to fourth rectangular prism cores 61 to 64, respectively. The magnetic fluxes Φ1 to Φ4 have the same amplitude.

Here, the case is shown where the U-phase voltage Vu leads the W-phase voltage Vw by 90° and the V-phase voltage Vv lags the W-phase voltage Vw by 90°, but even if the U-phase voltage Vu lags the W-phase voltage Vw by 90° and the V-phase voltage Vv leads the W-phase voltage Vw by 90°, the amplitude of the magnetic fluxes Φ1 to Φ4 will be the same.

As shown in FIG. 5(c), if there is a difference in the magnitude of the magnetic fluxes Φ1 to Φ4 passing through the first to fourth rectangular prism cores 61 to 64, it may be difficult to design an interphase decoupling transformer. In an ideal interphase decoupling transformer, the windings and core are designed so that the magnetic flux generated from the winding of one phase and interlinking with the windings of the other phases suppresses the electromotive force generated in the other windings. The shape and size of the core, such as the length of the core and the area of the cross section perpendicular to the longitudinal direction, are determined so as to have a magnetic resistance determined by the design, and there are design constraints on the shape and size of the core of an ideal interphase decoupling transformer.

Furthermore, in phase-to-phase non-interference transformers, the shape and size of the core are determined so as to avoid magnetic saturation. Therefore, if there is a difference in the magnitude of the magnetic flux passing through multiple cylindrical cores, it is necessary to determine the shape and size of each cylindrical core according to the one with the largest magnetic flux. Therefore, if there is a difference in the magnitude of the magnetic flux passing through multiple cylindrical cores, the overall core may become large.

For example, in the interphase decoupling transformer 38A shown in FIG. 3, the cross-sectional areas (areas of cross sections perpendicular to the longitudinal direction) of the first to fourth rectangular prism cores 61 to 64 are the same. As shown in FIG. 3, the amplitude of the magnetic fluxes Φ2 and Φ4 is larger than that of the magnetic fluxes Φ1 and Φ3, so the cross-sectional areas of the second and fourth rectangular prism cores 62 and 64 are determined to be large enough to avoid magnetic saturation, and the cross-sectional areas of the first and third rectangular prism cores 61 and 63 are matched to the cross-sectional areas of the second and fourth rectangular prism cores 62 and 64. In this way, the cross-sectional areas of the first to fourth rectangular prism cores 61 to 64 are matched to the cross-sectional areas of the second and fourth rectangular prism cores 62 and 64, which have larger magnetic fluxes, resulting in a larger overall core (each of the primary core 60-1 and the secondary core 60-2).

When the U-phase voltage Vu leads the W-phase voltage Vw by 90° and the V-phase voltage Vv lags the W-phase voltage Vw by 90°, the magnetic fluxes Φ1 to Φ4 have the same amplitude. Also, when the U-phase voltage Vu lags the W-phase voltage Vw by 90° and the V-phase voltage Vv leads the W-phase voltage Vw by 90°, the magnetic fluxes Φ1 to Φ4 have the same amplitude. In this way, by setting the lead and lag, or lag and lead, of the switching phase of the U-phase and V-phase relative to the W-phase to 90°, the magnetic fluxes Φ1 to Φ4 have the same amplitude. As a result, in a design that avoids magnetic saturation, the cross-sectional areas of the first rectangular prism core 61 to the fourth rectangular prism core 64 are the same, and the entire primary core 60-1 becomes smaller.

Figures 7(a) to (c) show the outline of each time waveform when a sinusoidal voltage is applied to the primary winding of each phase of the interphase decoupling transformer 38A shown in Figure 3. The U-phase voltage Vu lags the W-phase voltage Vw by 120°. The V-phase voltage Vv leads the W-phase voltage Vw by 120°. Figure 7(b) shows the outline of the time waveforms of the U-phase magnetic flux Φu, the V-phase magnetic flux Φv, and the W-phase magnetic flux Φw. Figure 7(c) shows the outline of the time waveforms of the magnetic fluxes Φ1 to Φ4 passing through the first square prism core 61 to the fourth square prism core 64, respectively. The amplitude of the magnetic fluxes Φ2 and Φ4 is larger than that of the magnetic fluxes Φ1 and Φ3.

Here, the case is shown in which the U-phase voltage Vu lags the W-phase voltage Vw by 120° and the V-phase voltage Vv leads the W-phase voltage Vw by 120°. However, even if the U-phase voltage Vu leads the W-phase voltage Vw by 120° and the V-phase voltage Vv lags the W-phase voltage Vw by 120°, the amplitude of the magnetic fluxes Φ2 and Φ4 will be greater than the amplitude of the magnetic fluxes Φ1 and Φ3.

Figure 8(a) shows the outline of the time waveforms of the U-phase voltage Vu, V-phase voltage Vv, and W-phase voltage Vw when the U-phase voltage Vu leads the W-phase voltage Vw by 90° and the V-phase voltage Vv lags the W-phase voltage Vw by 90°. Figure 8(b) shows the outline of the time waveforms of the U-phase magnetic flux Φu, V-phase magnetic flux Φv, and W-phase magnetic flux Φw. Figure 8(c) shows the outline of the time waveforms of the magnetic fluxes Φ1 to Φ4 passing through the first to fourth rectangular prism cores 61 to 64, respectively. The magnetic fluxes Φ1 to Φ4 have the same amplitude.

Here, the case is shown where the U-phase voltage Vu leads the W-phase voltage Vw by 90° and the V-phase voltage Vv lags the W-phase voltage Vw by 90°, but even if the U-phase voltage Vu lags the W-phase voltage Vw by 90° and the V-phase voltage Vv leads the W-phase voltage Vw by 90°, the amplitude of the magnetic fluxes Φ1 to Φ4 will be the same.

In this way, even when a sinusoidal voltage is applied to the primary windings of each phase, the amplitudes of the magnetic fluxes Φ1 to Φ4 are equalized by setting the lead and lag, or lag and lead, of the switching phase of the U and V phases relative to the W phase to 90°. As a result, in a design that avoids magnetic saturation, the cross-sectional areas of the first square prism core 61 to the fourth square prism core 64 are equalized, making the entire primary core 60-1 smaller.

Here, we have explained the relationship between the phase of the voltage applied to the primary windings of each phase and the overall size of the primary core 60-1, but the relationship between the phase of the voltage applied to the secondary windings of each phase and the overall size of the secondary core 60-2 is also similar.

Figure 9 shows the relationship between the maximum magnetic flux and the phase difference between phases for both rectangular wave excitation and sine wave excitation. The maximum magnetic flux 68 in the case of rectangular wave excitation is the maximum magnetic flux when the time waveform of the voltage applied to the winding of each phase is a rectangular wave. The maximum magnetic flux 69 in the case of sine wave excitation is the maximum magnetic flux when the time waveform of the voltage applied to the winding of each phase is a sine wave. The maximum magnetic flux is the maximum magnetic flux swing value of the first rectangular prism core 61 to the fourth rectangular prism core 64 that has the largest magnetic flux swing width, normalized by the swing width of the magnetic flux generated by the winding of one phase. However, the swing widths of the magnetic fluxes Φu, Φv, and Φw generated by the windings of each phase are calculated to be equal. The phase difference between phases indicates the leading phase value of the U-phase voltage Vu relative to the W-phase voltage Vw, and the lagging phase value of the V-phase voltage Vv relative to the W-phase voltage Vw. Alternatively, the phase difference between the phases indicates the lagging phase value of the U-phase voltage Vu relative to the W-phase voltage and the leading phase value of the V-phase voltage Vv relative to the W-phase voltage Vw.

In the case of square wave excitation, the maximum magnetic flux has a minimum value of 1 when the phase difference between the phases is 90°. And, when the phase difference between the phases is 60° and 120°, the maximum magnetic flux is 4/3 of the maximum value. In the case of sine wave excitation, the maximum magnetic flux has a minimum value of √2 when the phase difference between the phases is 90°. And, when the phase difference between the phases is 60° and 120°, the maximum magnetic flux is a maximum value of √3. Therefore, in both the case of square wave excitation and sine wave excitation, the phase difference between the phases may be greater than 60° and less than 120°. The phase difference between the phases may also be 90°.

Figure 10 shows a power conversion system 102 according to a first application embodiment of the present invention. In this system, the U-phase switching arm α2, the V-phase switching arm β2, and the W-phase switching arm γ2 of the second switching circuit 20 in the power conversion system 100 shown in Figure 1 are replaced with a U-phase diode arm αd, a V-phase diode arm βd, and a W-phase diode arm γd, respectively, and a smoothing reactor L is provided. Each diode arm includes an upper diode DH and a lower diode DL, and the anode electrode of the upper diode DH is connected to the cathode electrode of the lower diode DL. The cathode electrodes of the upper diode DH of each diode arm are commonly connected, and the anode electrodes of the lower diode DL are commonly connected. A smoothing reactor L is connected between the cathode electrode of the upper diode DH of each diode arm and the upper end of the capacitor arm CA2, and between the anode electrode of the lower diode DL of each diode arm and the lower end of the capacitor arm CA2. The voltage applied to the connection point between the upper diode DH and the lower diode DL in each diode arm is rectified by each diode arm, applied to the smoothing reactor L and the capacitor arm CA2, and applied to the second DC power source 36 after the harmonic components are suppressed.

Figure 11 shows a power conversion system 104 according to a second application embodiment of the present invention. This system is a power conversion system 100 shown in Figure 1, in which a resonance capacitor Cr is provided between the U-phase switching arm α1 and the U-phase primary winding 14u, between the V-phase switching arm β1 and the V-phase primary winding 14v, and between the W-phase switching arm γ1 and the W-phase primary winding 14w. Furthermore, the U-phase switching arm α2, the V-phase switching arm β2, and the W-phase switching arm γ2 of the second switching circuit 20B are replaced with the U-phase diode arm αd, the V-phase diode arm βd, and the W-phase diode arm γd, respectively. By providing the resonance capacitor Cr, the first switching circuit 10B operates as an LLC converter. The LLC converter is a converter that forms a resonance circuit with the inductance of the winding of the transformer and a capacitor connected to the transformer, and performs zero voltage switching by utilizing the resonance phenomenon. Losses are reduced by switching the switching element at the timing when the voltage applied to the switching element becomes zero.

Figure 12 shows a power conversion system 106 according to a third application embodiment of the present invention. In this system, a resonant capacitor Cr1 is provided between the U-phase switching arm α1 and the U-phase primary winding 14u, between the V-phase switching arm β1 and the V-phase primary winding 14v, and between the W-phase switching arm γ1 and the W-phase primary winding 14w in the power conversion system 100 shown in Figure 1. In addition, the U-phase switching arm α2, the V-phase switching arm β2, and the W-phase switching arm γ2 of the second switching circuit 20C are replaced with the U-phase diode arm αd, the V-phase diode arm βd, and the W-phase diode arm γd, respectively. Furthermore, a resonant capacitor Cr2 is provided between the U-phase diode arm αd and the U-phase secondary winding 24u, between the V-phase diode arm βd and the V-phase secondary winding 24v, and between the W-phase diode arm γd and the W-phase secondary winding 24w.

The primary winding structure 16 and the resonant capacitor Cr1 of each phase form a resonant circuit on the primary side of each phase. Similarly, the secondary winding structure 26 and the resonant capacitor Cr2 of each phase form a resonant circuit on the secondary side of each phase. Power is transmitted from the first switching circuit 10C to the second switching circuit 20C by resonance between the resonant circuit of each phase formed on the primary side and the resonant circuit of each phase formed on the secondary side.

Figure 13 shows a power conversion system 108 according to a second embodiment of the present invention. The power conversion system 108 performs switching of a phase selected from the U phase, V phase, and W phase in accordance with a power transmission command value in the power conversion system 100 shown in Figure 1, and stops switching of the other phases.

The power conversion system 108 includes a gate signal generating unit 70, a current control unit 72, and an operating phase determining unit 74 in addition to the first switching circuit 10 and the second switching circuit 20. The gate signal generating unit 70, the current control unit 72, and the operating phase determining unit 74 constitute a control unit that controls each switching arm. The operating phase determining unit 74 outputs designation information to the current control unit 72 and the gate signal generating unit 70 to designate which of the U-phase switching arms (α1, α2), V-phase switching arms (β1, β2), and W-phase switching arms (γ1, γ2) on the primary side and the secondary side should be switched based on the transmission power command value. For example, when the power transmission command value is equal to or less than a predetermined first threshold, the operating phase determining unit 74 selects the U-phase switching arms (α1, α2). When the power transmission command value exceeds the first threshold and is equal to or less than a predetermined second threshold, the operating phase determining unit 74 selects the U-phase switching arms (α1, α2) and the V-phase switching arms (β1, β2). The operating phase determination unit 74 further selects the U-phase switching arms (α1, α2), the V-phase switching arms (β1, β2), and the W-phase switching arms (γ1, γ2) when the power transmission command value exceeds a second threshold value.

The current control unit 72 determines the switching phase difference δ and duty ratio for the phase specified by the specification information based on the measured values of the primary side DC voltage Vin and the secondary side DC voltage Vout and the transmission power command value, and outputs them to the gate signal generation unit 70. The gate signal generation unit 70 generates a control signal that turns on and off the upper switching element SH and the lower switching element SL of the switching arm of the phase specified by the specification information, according to the switching phase difference δ and duty ratio for the phase specified by the specification information.

Figure 14 shows the relationship between the transmission power and the power transmission efficiency when the switching arm performing the switching is one-phase, two-phase, and three-phase. In operation per phase, as the transmission power increases from a certain value, the power transmission efficiency increases, and the power transmission efficiency is maximized at a certain peak transmission power. Then, when the transmission power increases beyond the peak transmission power, the power transmission efficiency decreases.

Therefore, when the switching arm performing the switching is two-phase, the peak transmission power is higher than when it is one-phase, and when it is three-phase, the peak transmission power is higher than when it is two-phase. Figure 14 shows peak transmission powers Pk1, Pk2, and Pk3 for the cases when the switching arm performing the switching is one-phase, two-phase, and three-phase, respectively. According to this embodiment, the number of phases performing the switching increases as the power transmission command value increases. This brings the power transmitted from the first switching circuit 10 to the second switching circuit 20 closer to the peak transmission power, improving power transmission efficiency.

A three-phase power conversion system has been shown above. The power conversion system may be configured as a single phase, two phase, or four or more phases. In this case, the number of switching arms and windings is provided according to the number of phases. For example, in the case of a two-phase system, the U-phase switching arm α1, the U-phase primary winding 14u, the U-phase switching arm α2, and the U-phase secondary winding 24u are removed from the power conversion system 100 shown in FIG. 1.

When using four phases, an additional switching arm is connected in parallel to the U-phase switching arm α1, the V-phase switching arm β1, and the W-phase switching arm γ1 of the power conversion system 100 shown in FIG. 1. An additional primary winding is then connected between the connection point between the upper switching element and the lower switching element of the additional switching arm and the common connection point of each of the other primary windings. Similarly, switching arms and secondary windings are added to the secondary side.

When the power conversion system has an N-phase configuration, where N is an integer equal to or greater than 2, the difference in switching phase between the N switching arms can be set to a value other than 360°/N to suppress the variation in the amplitude of the magnetic flux generated in the windings of each phase.

10, 10B, 10C First switching circuit, 12p, 22p Positive terminal, 12n, 22n Negative terminal, 14u U-phase primary winding, 14v V-phase primary winding, 14w W-phase primary winding, 16 Primary winding structure, 20, 20A, 20B, 20C Second switching circuit, 24u U-phase secondary winding, 24v V-phase secondary winding, 24w W-phase secondary winding, 26 Secondary winding structure, 30 First DC power source, 32 Commercial power source system, 34 AC/DC converter, 36 Second DC power source, 38 Three-phase transformer, 38A, 38N Interphase decoupling transformer, 40-1, 60-1 Primary core, 40-2, 60-2 Secondary core, 41 First vertical core, 42 Second vertical core, 43 third vertical core, 44 fourth vertical core, 46 horizontal core, 61 first rectangular prism core, 62 second rectangular prism core, 63 third rectangular prism core, 64 fourth rectangular prism core, 66 plate core, 68 maximum magnetic flux in case of rectangular wave excitation, 69 maximum magnetic flux in case of sine wave excitation, 70 gate signal generating unit, 72 current control unit, 74 operation phase determining unit, α1, α2 U-phase switching arm, β1, β2 V-phase switching arm, γ1, γ2 W-phase switching arm, SH upper switching element, SL lower switching element, CA1, CA2 capacitor arm, C1 upper capacitor, C2 lower capacitor, αd U-phase diode arm, βd V-phase diode arm, γd W-phase diode arm, Cr, Cr1, Cr2 resonant capacitor, L smoothing reactor.

Claims (8)

A switching circuit including an A-phase winding, a B-phase winding, and a C-phase winding,
the A-phase winding, the B-phase winding, and the C-phase winding form an inter-phase non-interference winding structure;
The switching circuit includes:
the phase of the voltage between the terminals of the A-phase winding leads the phase of the voltage between the terminals of the C-phase winding by a range of more than 60° and less than 120°;
switching voltages applied to the A-phase winding, the B-phase winding, and the C-phase winding, respectively, such that a phase of a voltage between the terminals of the B-phase winding lags a phase of a voltage between the terminals of the C-phase winding in a range of more than 60° and less than 120°;
or,
the phase of the voltage between the terminals of the A-phase winding lags behind the phase of the voltage between the terminals of the C-phase winding in a range of more than 60° and less than 120°;
a contactless power transmission circuit which switches voltages applied to the A-phase winding, the B-phase winding, and the C-phase winding, respectively, so that the phase of the terminal voltage of the B-phase winding leads the phase of the terminal voltage of the C-phase winding by a range of more than 60° and less than 120°. 2. The non-contact power transmission circuit according to claim 1,
The switching circuit includes:
the phase of the voltage across the A-phase winding leads the phase of the voltage across the C-phase winding by 90°;
switching voltages applied to the A-phase winding, the B-phase winding, and the C-phase winding, respectively, such that a phase of a voltage between the terminals of the B-phase winding lags a phase of a voltage between the terminals of the C-phase winding by 90°;
or,
the phase of the voltage across the A-phase winding lags behind the phase of the voltage across the C-phase winding by 90°;
a contactless power transmission circuit which switches voltages applied to the A-phase winding, the B-phase winding, and the C-phase winding, respectively, so that the phase of the terminal voltage of the B-phase winding leads the phase of the terminal voltage of the C-phase winding by 90°. an A-phase switching arm, a B-phase switching arm, and a C-phase switching arm connected in parallel, each of the A-phase switching arm, the B-phase switching arm, and the C-phase switching arm including an upper switching element and a lower switching element, one end of which is commonly connected;
an A-phase winding provided for the A-phase switching arm, the A-phase winding having one end connected to a connection point of the upper switching element and the lower switching element included in the A-phase switching arm;
a B-phase winding provided for the B-phase switching arm, the B-phase winding having one end connected to a connection point of the upper switching element and the lower switching element included in the B-phase switching arm;
a C-phase winding provided for the C-phase switching arm, the C-phase winding having one end connected to a connection point of the upper switching element and the lower switching element included in the C-phase switching arm;
The A-phase winding, the B-phase winding, and the C-phase winding are
Forming a phase-to-phase non-interference winding structure,
a common power source or load is connected to the other ends of the A-phase winding, the B-phase winding and the C-phase winding, respectively. 4. The non-contact power transmission circuit according to claim 3,
a switching phase of the A-phase switching arm leads a switching phase of the C-phase switching arm by a range of more than 60° and less than 120°, and a switching phase of the B-phase switching arm lags a switching phase of the C-phase switching arm by a range of more than 60° and less than 120°,
Alternatively, the non-contact power transmission circuit is characterized in that the switching phase of the A-phase switching arm lags behind the switching phase of the C-phase switching arm in a range of more than 60° and less than 120°, and the switching phase of the B-phase switching arm leads behind the switching phase of the C-phase switching arm in a range of more than 60° and less than 120°. 5. The non-contact power transmission circuit according to claim 4,
a switching phase of the A-phase switching arm leads a switching phase of the C-phase switching arm by 90°, and a switching phase of the B-phase switching arm lags a switching phase of the C-phase switching arm by 90°;
Alternatively, the non-contact power transmission circuit is characterized in that the switching phase of the A-phase switching arm lags behind the switching phase of the C-phase switching arm by 90°, and the switching phase of the B-phase switching arm leads the switching phase of the C-phase switching arm by 90°. The non-contact power transmission circuit according to any one of claims 1 to 5,
a first core and a second core passing through a forward wound loop and a reverse wound loop of the A-phase winding, respectively;
a third core and a fourth core passing through a forward wound loop and a reverse wound loop of the B-phase winding, respectively;
the first core and the second core, which pass through the A-phase winding, pass through the forwardly wound loop of the C-phase winding;
A non-contact power transmission circuit, characterized in that the third core and the fourth core passing through the B-phase winding pass through a reverse-wound loop of the C-phase winding. 7. The non-contact power transmission circuit according to claim 6, wherein each of the first core to the fourth core is formed in a rod shape.
A contactless power transmission circuit comprising a common core commonly coupled to one end of each of the first core to the fourth core. a plurality of switching arms connected in parallel, each of the switching arms including an upper switching element and a lower switching element, one end of which is commonly connected;
a winding provided for each of the switching arms, the winding having one end connected to a connection point between the upper switching element and the lower switching element;
A control unit for controlling each of the switching arms,
The other ends of the windings are connected in common,
A common power source or load is connected to the other end of each of the windings;
each of the windings is coupled to a corresponding one of a plurality of external windings of an external switching circuit;
The plurality of windings provided corresponding to the plurality of switching arms form an inter-phase non-interference winding structure,
The control unit is
A non-contact power transmission circuit, comprising: a contactless power transmission circuit that causes a number of the switching arms, among the plurality of switching arms, to perform switching in accordance with a command value for transmission power to the switching circuit.

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