Bidirectional power grid interconnection device

Abstract

To provide a bidirectional AC / DC power grid interconnection device and a multi-phase transformer that do not require automatic control by an electronic control unit and operate autonomously.SOLUTION: A bidirectional power interconnection device that interconnects an AC power portion and a DC power portion in both directions includes a multiphase transformer that converts the three-phase AC of the AC power portion into a 3n-phase multiphase AC, a first full-wave rectification portion that has a plurality of first rectification elements that can full-wave rectify the multiphase AC on the secondary side of the multiphase transformer and output it to the DC power portion, a second full-wave rectification portion that has a plurality of second rectification elements that can full-wave rectify the multiphase AC on the secondary side of the multiphase transformer and output it to a resistance element, and a switch portion that has a plurality of switch elements that are respectively parallel to the plurality of first rectification elements, the switch elements are respectively associated with the plurality of second rectification elements and are switched so as to be off when the associated second rectification element is non-conducting and on when the associated second rectification element is conducting.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a bidirectional power interconnection device that performs bidirectional power conversion between AC and DC, and a multi-phase transformer used therein. [Background technology]

[0002] There is known a bidirectional power grid-connected device that performs power conversion between a commercial AC power system and DC power equipment such as a power generation system and a storage battery. Patent Document 1 discloses a system in which a wind power generation system and a storage battery are connected to a power company system via a grid-connected inverter.

[0003] In Patent Documents 2 and 3, although not bidirectional, a multiphase transformer is used when rectifying AC and converting it to DC without using an AC / DC converter, thereby solving the problem of high-frequency switching noise. As a method for connecting the secondary terminals of the transformer, Patent Document 2 proposes a star connection, while Patent Document 3 proposes a modified connection based on a delta connection. These modified connections solve the problem of large transformers caused by providing independent windings for each phase of the multiphase transformer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-250227 A [Patent Document 2] Patent Publication No. 2022-71713 [Patent Document 3] JP 2022-540927 A Summary of the Invention [Problem to be solved by the invention]

[0005] In conventional AC / DC bidirectional interconnection technology such as that in Patent Document 1, an electronic control unit such as a control IC is required for electronic control of the bidirectional converter, etc. In addition, in the AC / DC interconnection using a multiphase transformer in Patent Documents 2 and 3, the output of the multiphase transformer is full-wave rectified and converted to DC, but a full-wave rectifier circuit alone cannot realize a bidirectional interconnection.

[0006] In view of the above, an object of the present invention is to provide a device and a multi-phase transformer that perform bidirectional AC / DC power interconnection by autonomous operation without the need for automatic control by an electronic control unit. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides the following configuration. A first aspect of the present invention is a bidirectional power interconnection device that bidirectionally interconnects an AC power section and a DC power section, a multi-phase transformer that converts the three-phase AC power from the AC power unit into a multi-phase AC power of 3n phases (n is a natural number equal to or greater than 2); a first full-wave rectification unit including a plurality of first rectification elements capable of full-wave rectifying the multi-phase AC on the secondary side of the multi-phase transformer and outputting the full-wave rectified AC to the DC power unit; a second full-wave rectification unit including a plurality of second rectification elements capable of full-wave rectifying the multi-phase AC on the secondary side of the multi-phase transformer and outputting the full-wave rectified AC to a resistance element; a plurality of switch elements each in parallel with a respective one of the plurality of first rectifying elements, each switch element being in parallel with a respective one of the plurality of second rectifying elements; It is related , relationship When the second rectifying element is non-conducting, , the related switch elements are It is off , and the associated second rectifying element is Continuity When the switch element is turned on, a drive signal for driving the switch element is output, thereby turning on the switch element. and a switch section that switches between the first and second inputs. In the above aspect, The plurality of first rectifying elements of the first full-wave rectifying unit include 3n first positive-side rectifying elements each having an anode connected to each secondary-side terminal of the multi-phase transformer and a cathode commonly connected to a positive terminal of the DC power section; a first negative-side rectifier element having a cathode connected to each secondary-side terminal of the multi-phase transformer and an anode commonly connected to a negative terminal of the DC power section; The plurality of second rectifying elements of the second full-wave rectifying unit include 3n second positive-side rectifying elements, each having an anode connected to each secondary-side terminal of the multi-phase transformer and a cathode commonly connected to one end of the resistor element; and 3n second negative-side rectifying elements, the cathodes of which are connected to the secondary terminals of the multi-phase transformer and the anodes of which are commonly connected to the other end of the resistive element. In the above aspect, A drive unit that switches the switch element on and off includes: a light-emitting element that is connected in series with the second rectifying element and emits light only when the second rectifying element is conductive, and a light-receiving element that receives light from the light-emitting element, The light receiving element outputs a drive signal that turns the switch element on when it receives light from the light emitting element and turns it off when it does not receive light. In the above aspect, the first rectifying element is a parasitic diode of a field effect transistor or a diode connected in parallel with the parasitic diode, The switch element is a current path between the drain and source of the field effect transistor, and the gate of the field effect transistor is driven by a drive signal from the drive section. In the above aspect, the multi-phase transformer has first to third main terminals and fourth to 3n sub-terminals as secondary side terminals, and outputs, as line voltages between predetermined secondary side terminals, a first three-phase AC and second to nth three-phase ACs each delayed in phase by 60 / n degrees, 2×(60 / n) degrees,..(n-1)×(60 / n) degrees from each phase of the first three-phase AC. In one embodiment of the secondary winding, two or more mutually separated main windings are connected between the first and second main terminals, the second and third main terminals, and the third and first main terminals, respectively, which generate the first three-phase AC; Between the two main windings of one phase, two auxiliary windings of the other two phases are V-connected, and a connection point between the two auxiliary windings is connected to one of the sub-terminals; The multiple main windings and multiple auxiliary windings included in each of the three winding groups arranged between the first and second main terminals, between the second and third main terminals, and between the third and first main terminals, respectively, are consistent in relative phase relationship, relative number of turns, and connection relationship between the windings. In another embodiment of the secondary winding, two or more mutually separated main windings are connected between the first and second main terminals, the second and third main terminals, and the third and first main terminals, respectively, to generate the first three-phase AC; Between the two main windings of one phase, two auxiliary windings of the other two phases are V-connected, and a connection point between the two auxiliary windings is connected to one of the sub-terminals; A single auxiliary winding of one of the other two phases is connected between one or more branch points of the main winding of one phase and one or more of the sub-terminals; The multiple main windings and multiple auxiliary windings included in each of the three winding groups arranged between the first and second main terminals, between the second and third main terminals, and between the third and first main terminals, respectively, are consistent in relative phase relationship, relative number of turns, and connection relationship between the windings. In yet another embodiment of the secondary winding, one main winding is connected between the first and second main terminals, the second and third main terminals, and the third and first main terminals to generate the first three-phase AC current; A single auxiliary winding of one of the other two phases is connected between one or more branch points of the main winding of one phase and one or more of the sub-terminals; The main winding and one or more auxiliary windings included in each of the three winding groups arranged between the first and second main terminals, between the second and third main terminals, and between the third and first main terminals, respectively, are consistent in relative phase relationship, relative number of turns, and connection relationship between the windings.

[0008] Another aspect of the present invention is a multi-phase transformer that converts three-phase AC into 3n-phase polyphase AC (n is a natural number equal to or greater than 2), and has first to third main terminals and fourth to 3n-th sub-terminals as secondary side terminals, and outputs, as line-to-line voltages between predetermined secondary side terminals, a first three-phase AC and second to n-th three-phase ACs each delayed in phase by 60 / n degrees, 2×(60 / n) degrees,..(n-1)×(60 / n) degrees from each phase of the first three-phase AC. In one embodiment of the secondary winding, two or more mutually separated main windings are connected between the first and second main terminals, the second and third main terminals, and the third and first main terminals, respectively, which generate the first three-phase AC; Between the two main windings of one phase, two auxiliary windings of the other two phases are V-connected, and a connection point between the two auxiliary windings is connected to one of the sub-terminals; The multiple main windings and multiple auxiliary windings included in each of the three winding groups arranged between the first and second main terminals, between the second and third main terminals, and between the third and first main terminals, respectively, are consistent in relative phase relationship, relative number of turns, and connection relationship between the windings. In another embodiment of the secondary winding, two or more mutually separated main windings are connected between the first and second main terminals, the second and third main terminals, and the third and first main terminals, respectively, to generate the first three-phase AC; Between the two main windings of one phase, two auxiliary windings of the other two phases are V-connected, and a connection point between the two auxiliary windings is connected to one of the sub-terminals; A single auxiliary winding of one of the other two phases is connected between one or more branch points of the main winding of one phase and one or more of the sub-terminals; The multiple main windings and multiple auxiliary windings included in each of the three winding groups arranged between the first and second main terminals, between the second and third main terminals, and between the third and first main terminals, respectively, are consistent in relative phase relationship, relative number of turns, and connection relationship between the windings. In yet another embodiment of the secondary winding, one main winding is connected between the first and second main terminals, the second and third main terminals, and the third and first main terminals to generate the first three-phase AC current; A single auxiliary winding of one of the other two phases is connected between one or more branch points of the main winding of one phase and one or more of the sub-terminals; The main winding and one or more auxiliary windings included in each of the three winding groups arranged between the first and second main terminals, between the second and third main terminals, and between the third and first main terminals, respectively, are consistent in relative phase relationship, relative number of turns, and connection relationship between the windings. Effect of the Invention

[0009] According to the present invention, a device and a multi-phase transformer are realized that perform bidirectional AC / DC power interconnection through autonomous operation without the need for automatic control by an electronic control unit. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a schematic diagram of an overall configuration including a bidirectional power interconnection device. [Diagram 2] FIG. 2 shows an example of a specific configuration of the interconnection circuit unit in FIG. [Diagram 3] FIG. 3 shows another example of the switch element of FIG. [Figure 4] 4(a) and (b) show an example of the operation of the interconnection circuit unit at point x of the waveform in FIG. 6(a). [Diagram 5] 5(a) and (b) show an example of the operation of the interconnection circuit unit at point y of the waveform in FIG. 6(a). [Figure 6] FIG. 6(a) shows the voltage waveform of a 12-phase AC current, and (b) shows the full-wave rectified waveform of the 12-phase AC voltage waveform shown in (a). [Figure 7] 7(a) is a diagram showing the relationship between the 12 terminals on the secondary side of a 12-phase transformer and the 12 line voltages, while (b) is a vector diagram showing the phase relationship of the line voltages. [Figure 8] FIG. 8 shows the waveform of a three-phase AC current observed on the primary side of a multi-phase transformer when the storage battery shown in FIG. 4(b) and FIG. 5(b) is discharged. [Figure 9]FIG. 9 is a diagram illustrating a schematic configuration of the multi-phase transformer illustrated in FIG. [Figure 10] FIG. 10(a) is a detailed vector diagram of the secondary winding in FIG. 9, and the table in (b) shows example numerical values ​​of the line voltages of the first three-phase AC and the phase voltages of each winding in (a). [Figure 11] FIG. 11 is a winding connection diagram of a polyphase transformer based on the vector diagram of FIG. [Figure 12] 12(a) to (j) show variations of the secondary side connections of the 12-phase transformer shown in FIG. 10(a). [Figure 13] FIG. 13(a) shows another example of a multi-phase transformer, and the table in (b) shows example numerical values ​​of the line voltages of a first three-phase AC current and the phase voltages of each winding in (a). [Figure 14] Figure 14(a) is a vector diagram similar to Figure 10(a) showing another example of the secondary side wiring of a multi-phase transformer, and (b) is a vector diagram of the line voltage on the secondary side. [Figure 15] Figure 15(a) is a vector diagram similar to Figure 10(a) showing yet another example of secondary side wiring of a multi-phase transformer, and (b) is a vector diagram of the line voltage on the secondary side. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of a bidirectional power grid-connection device according to the present invention will be described with reference to the drawings. In this specification, "three-phase AC" refers to symmetrical three-phase AC. Symmetrical three-phase AC is composed of three sine waves that are equal in magnitude and frequency and have a phase difference of 120 degrees from each other.

[0012] (1) Configuration and operation of the interconnection circuit FIG. 1 is a diagram showing a schematic diagram of an overall configuration including a bidirectional power interconnection device. The bidirectional power interconnection device is a device for bidirectionally supplying and demanding power between an AC power section and a DC power section. The AC power section here is assumed to be system power in which three-phase AC flows through lines R0, S0, and T0. The DC power section here is assumed to be a storage battery 5. A DC power generation facility such as a solar power generation system can also be further connected to the storage battery 5. The bidirectional power interconnection device has a multi-phase transformer 1 and an interconnection circuit section 10.

[0013] The primary winding of the multi-phase transformer 1 is connected to three-phase lines R0, S0, and T0 of the system power. The multi-phase transformer 1 in FIG. 1 converts the three-phase AC on the primary side into 12-phase polyphase AC and outputs it from 12 secondary terminals R1...T4. Each of the 12-phase AC voltages is a line voltage output between a predetermined two terminals among the 12 secondary terminals R1...T4, and consists of four sets of three-phase AC. FIG. 6(a) shows the waveform of the 12-phase AC voltage. The detailed configuration of the multi-phase transformer 1 will be described later.

[0014] The interconnection circuit unit 10 is shown diagrammatically in Fig. 1. The interconnection circuit unit 10 has a function of full-wave rectifying the output of the multi-phase transformer 1 and outputting the result to the storage battery 5, and a function of outputting power from the storage battery 5 to the secondary terminal of the multi-phase transformer 1. The interconnection circuit unit 10 has 12 positive side circuits 11 of the same configuration connected to each of the secondary terminals R1..T4 of the multi-phase transformer 1, and 12 negative side circuits 12 of the same configuration.

[0015] The terminal R1 will be taken as an example. The anode of the first positive-side rectifier P1 and the anode of the second positive-side rectifier P2 of the positive-side circuit 11 are connected to the terminal R1. Furthermore, the cathode of the first negative-side rectifier N1 and the cathode of the second negative-side rectifier N2 of the negative-side circuit 12 are connected to the terminal R1. The "anode" is a positive electrode, which is an electrode into which a current flows. The "cathode" is a negative electrode, which is an electrode from which a current flows out. The "rectifier element" is typically a diode. However, the first positive-side rectifier P1 and the first negative-side rectifier N1 may be rectifier elements that are not independent elements but are incorporated as part of other elements. Such a rectifier element may be, for example, a parasitic diode of a field-effect transistor (FET).

[0016] The cathode of the first positive-side rectifier element P1 is connected to the positive electrode connection terminal 6 of the storage battery 5, and the anode of the first negative-side rectifier element N1 is connected to the positive electrode connection terminal 6 of the storage battery 5. 5 The negative electrode connection terminal 7 is connected to the negative electrode connection terminal 7.

[0017] The cathode of the second positive-side rectifier element P2 is connected to one end of the resistor element 4, and the anode is connected to the other end of the resistor element 4. Note that a line between the cathode of the second positive side rectifier element P2 and one end of the resistor element 4 and a line between the cathode of the second negative side rectifier element N2 and one end of the resistor element 4 are connected to the other end of the resistor element 4. anode A photovoltaic photodiode, which will be described later, is inserted and connected in the forward direction between the first end of the first positive-side rectifier element P2 and the other end of the resistance element 4. However, since this does not affect the functions of the second positive-side rectifier element P2 and the second negative-side rectifier element N2, the case in which it is indirectly connected to the resistance element 4 in this manner is still referred to as being "connected."

[0018] Furthermore, the first positive-side rectifier element P1 and the first negative-side rectifier element N1 are each connected in parallel to a switch element SW. The "switch element" here includes an element that has a control end and a current path and can switch the current path between non-conduction and conduction when the control end is driven. Such an element is, for example, a semiconductor element such as an FET, a bipolar transistor, or an IGBT.

[0019] The switch element SW in parallel with the first positive side rectifier P1 switches to be off when the associated second positive side rectifier P2 is not conducting and to be on when the associated second positive side rectifier P2 is conducting. Similarly, the switch element SW in parallel with the first negative side rectifier N1 switches to be off when the associated second negative side rectifier N2 is not conducting and to be on when the associated second negative side rectifier N2 is conducting. Each switch element SW has a driver for driving its control end. In FIG. 1, a part of the driver of each switch element SW is simply represented by a photodiode connected in series with the second positive side rectifier P2 and the second negative side rectifier N2, respectively. The operation mechanism of this switch element SW will be described in detail later.

[0020] Circuits having the same configuration as above are connected between each of the other secondary side terminals R2..T4 and the storage battery 5, and between the other secondary side terminals R2..T4 and the resistance element 4, respectively.

[0021] Generally speaking, the twelve first positive-side rectifier elements P1 have their anodes connected to the secondary terminals R1...T4, respectively, and their cathodes connected in common to the positive electrode connection terminal 6 of the storage battery 5. The twelve first negative-side rectifier elements N1 have their cathodes connected to the secondary terminals R1...T4, respectively, and their anodes connected in common to the negative electrode connection terminal 7 of the storage battery 5. Therefore, the twelve first positive-side rectifier elements P1 and the twelve first negative-side rectifier elements N1 constitute a first full-wave rectifier unit that full-wave rectifies the multi-phase AC on the secondary side of the multi-phase transformer 1 and outputs it to the storage battery 5.

[0022] Similarly, the twelve second positive-side rectifier elements P2 have their anodes connected to the secondary terminals R1..T4, respectively, and their cathodes commonly connected to one end of the resistor element 4. The twelve second negative-side rectifier elements N2 have their cathodes connected to the secondary terminals R1..T4, respectively, and their anodes commonly connected to the other end of the resistor element 4. Therefore, the twelve second positive-side rectifier elements P2 and the twelve second negative-side rectifier elements N2 constitute a second full-wave rectifier unit that full-wave rectifies the multi-phase AC on the secondary side of the multi-phase transformer 1 and outputs it to the resistor element 4.

[0023] The rectification operations of the first full-wave rectifier and the second full-wave rectifier are basically the same, with the difference being that the output destination is either the storage battery 5 or the resistive element 4. In the rectification operation, a full-wave rectified current can flow only between the two terminals that output the maximum voltage among the 12 line voltages output from the secondary terminals R1..T4, i.e., between the secondary terminal with the highest potential and the secondary terminal with the lowest potential.

[0024] However, in the first full-wave rectifier, when the potential of the secondary terminal of the multi-phase transformer 1 is lower than the potential of the positive electrode connection terminal 6 of the storage battery 5, no current can flow from the multi-phase transformer 1 to the storage battery 5. Also, at this time, in the first full-wave rectifier, the positive side rectifier element P1 and the negative side rectifier element N1 are in the reverse direction, so that no current can flow from the storage battery 5 to the multi-phase transformer 1 either.

[0025] Therefore, in the present invention, the current flowing through the second full-wave rectifier is used as a trigger to turn on the switch element SW, thereby bypassing the rectifier elements P1 and N1 of the first full-wave rectifier, and allowing the current to flow from the storage battery 5 to the multi-phase transformer 1 through the switch element SW. The second full-wave rectifier is provided to operate the switch element SW. This mechanism realizes bidirectional interconnection between the AC power unit and the DC power unit. Moreover, this mechanism is realized autonomously by only the circuit elements of the interconnection circuit unit 10, and does not require automatic control by an electronic control unit.

[0026] The main current for supplying and demanding power between the multi-phase transformer 1 and the storage battery 5 flows through the first full-wave rectifier circuit. The second full-wave rectifier circuit is a current detection circuit for driving each switch element SW of the switch section, so it is sufficient for a current required for detection to flow. Therefore, the resistance value of the resistive element 4, which is the load of the second full-wave rectifier circuit, is set according to the current detection sensitivity.

[0027] Fig. 2 shows an example of a specific configuration of the interconnection circuit unit 10 in Fig. 1. Fig. 2 shows only a circuit connected between secondary side terminals R1 and S1 that outputs one line voltage V1r (see Fig. 6(a)).

[0028] The positive-side circuit 11r connected to the secondary-side terminal R1 will be described. The switch element SWpr is an N-channel MOS field-effect transistor (MOSFET). The drain of this MOSFET is connected to the positive electrode of the storage battery 5, and the source is connected to the terminal R1. The parasitic diode of the MOSFET corresponds to the positive-side rectifier element P1r in the first full-wave rectifier. Here, an external diode is connected in parallel with the parasitic diode, and this also plays the role of the positive-side rectifier element P1r. When the switch element is a MOSFET, this external diode is not essential.

[0029] Furthermore, the anode of the diode, which is the positive-side rectifier element P2r of the second full-wave rectifier, is connected to the terminal R1, and the cathode is connected to one end of the input side of the photovoltaic element PVpr. The other end of the input side of the photovoltaic element PVpr is connected to one end of the resistor element 4. Thus, the photodiode, which is the light-emitting element on the input side of the photovoltaic element PVpr, is inserted and connected in series with the positive-side rectifier element P2r, and emits light when it detects a current flowing through the positive-side rectifier element P2r. The light-receiving diode on the output side of the photovoltaic element PVpr outputs a predetermined current to the outside when the photodiode on the input side emits light. The output current of the photovoltaic element PVpr generates a gate drive voltage for the switch element SWpr, which is a MOSFET, by flowing through the resistor element 8. In this way, when the positive-side rectifier element P2r is conductive, the photovoltaic element PVpr outputs a drive signal to the drive unit of the switch element SWpr.

[0030] The positive side circuit 11s connected to the secondary side terminal S1 has exactly the same configuration as the above-mentioned positive side circuit 11r.

[0031] Next, the negative side circuit 12r connected to the secondary side terminal R1 will be described. The switch element SWnr is an N-channel MOSFET. The drain of this MOSFET is connected to the terminal R1, and the source is connected to the positive electrode of the storage battery 5. The parasitic diode of the MOSFET corresponds to the negative side rectifier element N1r in the first full-wave rectifier. Here, an external diode is connected in parallel with the parasitic diode, and this also plays the role of the negative side rectifier element N1r. Note that this external diode is not essential.

[0032] Furthermore, the anode of the diode, which is the negative rectifier element N2r of the second full-wave rectifier, is connected to one end of the input side of the photovoltaic PVnr, and the cathode is connected to the terminal R1. The other end of the input side of the photovoltaic PVnr is connected to the other end of the resistor element 4. Therefore, the photodiode, which is the light-emitting element on the input side of the photovoltaic PVnr, is inserted and connected in series with the negative rectifier element N2r, and emits light when it detects a current flowing through the negative rectifier element N2r. The light-receiving diode on the output side of the photovoltaic PVnr outputs a predetermined current to the outside when the photodiode on the input side emits light. The output current of the photovoltaic PVnr generates a gate drive voltage for the switch element SWnr, which is a MOSFET, by flowing through the resistor element 8. In this way, when the negative rectifier element N2r is conductive, the photovoltaic PVnr outputs a drive signal to the drive unit of the switch element SWnr.

[0033] The negative side circuit 12s connected to the secondary side terminal S1 has exactly the same configuration as the negative side circuit 12r described above.

[0034] Fig. 3 shows another example of the switch elements SWpr, SWnr, SWps, and SWns in Fig. 2. When the switch elements are IGBTs or bipolar transistors, external diodes are essential for passing a current in the opposite direction to the current that flows when the switch elements are conductive. The external diodes function as the positive-side rectifier elements P1r, P1s or the negative-side rectifier elements N1r, N1s of the first full-wave rectifier.

[0035] Figures 4(a) and (b) show the operation of the interconnection circuit unit 10 at time x of the waveform in Figure 6(a). At time x, the line voltage V1r between the R1 terminal and the S1 terminal is at a maximum (the R1 terminal is at a high potential, and the S1 terminal is at a low potential), and therefore the R1 terminal has the highest potential among the 12 secondary side terminals.

[0036] 4(a) shows a case where the potential of the R1 terminal is higher than the potential of the positive electrode of the storage battery 5. A current I1 flows through the thick-line path in the first full-wave rectifier circuit, and a current I2 flows through the thin-line path in the second full-wave rectifier circuit, passing through the resistive element 4. The current I2 flows through the positive-side rectifier element P2r and the negative-side rectifier element N2s, turning on the switch elements SWpr and SWns. In this case, the positive-side rectifier element P1r and the negative-side rectification Since element N1s is forward-direction relative to the current I1, the current I1 for charging the storage battery 5 can flow from terminal R1 to the positive electrode of the storage battery 5, and from the negative electrode of the storage battery 5 to terminal S1, regardless of whether the switch elements SWpr and SWns are on or off.

[0037] 4B shows a case where the potential of the positive electrode of the storage battery 5 is higher than the potential of the R1 terminal. rectification The element N1s is in the reverse direction. Meanwhile, in the second full-wave rectifier circuit, a current I2 flows through the resistor element 4 in the same direction as in FIG. 4(a). The current I2 flows through the positive-side rectifier element P2r and the negative-side rectifier element N2s, turning on the switch elements SWpr and SWns. As a result, the current I1 can flow through the switch elements SWpr and SWns. rectification The element N1s is bypassed by the switch elements SWpr and SWns.

[0038] Figures 5(a) and (b) show an example of the operation of the interconnection circuit unit 10 at time y of the waveform in Figure 6(a). At time y, the line voltage V1r between the R1 terminal and the S1 terminal is at a maximum (the S1 terminal is at a high potential, and the R1 terminal is at a low potential), and therefore the S1 terminal is at the highest potential among the 12 secondary side terminals.

[0039] 5(a) shows a case where the potential of the S1 terminal is higher than the potential of the positive electrode of the storage battery 5. A current I1 flows through the thick-line path in the first full-wave rectifier circuit, and a current I2 flows through the thin-line path in the second full-wave rectifier circuit, passing through the resistance element 4. The current I2 flows through the positive-side rectifier element P2s and the negative-side rectifier element N2r, turning on the switch elements SWps and SWnr. In this case, the positive-side rectifier element P1s and the negative-side rectification Since element N1r is forward with respect to the current I1, the current I1 for charging the storage battery 5 can flow from terminal S1 to the positive electrode of the storage battery 5, and from the negative electrode of the storage battery 5 to terminal R1, regardless of whether the switch elements SWps and SWnr are on or off.

[0040] 5B shows a case where the potential of the positive electrode of the storage battery 5 is higher than the potential of the S1 terminal. rectification The element N1r is in the reverse direction. Meanwhile, in the second full-wave rectifier circuit, a current I2 flows through the resistor element 4 in the same direction as in FIG. 5(a). The current I2 flows through the positive-side rectifier element P2s and the negative-side rectifier element N2r, turning on the switch elements SWps and SWnr. As a result, the current I1 can flow through the switch elements SWps and SWnr. rectification The element N1r is bypassed by the switch elements SWps and SWnr.

[0041] FIG. 6(b) shows a waveform obtained by full-wave rectifying the 12-phase AC voltage waveform shown in FIG. 6(a). This is the voltage waveform across the storage battery 5 when the storage battery 5 is charged as shown in FIG. 4(a) and FIG. 5(a). The maximum voltage of the 12 line voltages V1r to V4t output from the secondary terminals R1 to T4 of the 12-phase transformer alternates every 15 degrees of phase, and current flows from the terminal with the highest potential to the terminal with the lowest potential through the first full-wave rectifier circuit. The more phases in the multi-phase transformer, the smaller the pulsation of the rectified waveform becomes, and the closer it becomes to a completely direct current.

[0042] 7(a) is a diagram showing the corresponding relationship between the 12 terminals R1-T4 on the secondary side of a 12-phase transformer and the 12 line voltages Vr1-Vt4. (b) is a vector diagram showing the phase relationship of the 12 line voltages Vr1-Vt4 (clockwise is the leading direction). The 12 line voltages Vr1-Vt4 consist of four sets of three-phase AC, first to fourth, as follows. The numbers in parentheses indicate which terminal the line voltage is between. First three-phase AC: V1r (between R1 and S1), V1s (between S1 and T1), V1t (between T1 and R1) - Second three-phase AC: V2r (between R1 and R3), V2s (between S1 and S3), V2t (between T1 and T3) Third three-phase AC: V3r (between R1 and R2), V3s (between S1 and S2), V3t (between T1 and T2) Fourth three-phase AC: V4r (between R1 and R4), V4s (between S1 and S4), V4t (between T1 and T4)

[0043] The second three-phase AC, the third three-phase AC, and the fourth three-phase AC are phase-delayed by 15 degrees, 30 degrees, and 45 degrees, respectively, relative to the first three-phase AC.

[0044] Fig. 8 shows a measured waveform of three-phase AC output to the primary side of the multi-phase transformer 1 when discharging from the storage battery 5 to the multi-phase transformer 1 as shown in Fig. 4(b) and Fig. 5(b). According to the bidirectional power interconnection device of the present invention, a stable three-phase AC waveform can be generated from the DC power section by the autonomous operation of the interconnection circuit section itself without automatic control by an electronic control unit, and power can be supplied to the grid. This reduces adverse effects on the grid.

[0045] (2) Structure and operation of multi-phase transformer Fig. 9 is a diagram showing a schematic configuration of the multi-phase transformer 1 shown in Fig. 1. In this vector diagram, one line segment represents one winding, the length of the line segment corresponds to the number of turns of the winding, i.e., the electromotive force (phase voltage) of the winding, the black circle indicates the polarity of the winding, and the angle between the line segments indicates the phase relationship of the phase voltages (this is also true for the vector diagrams below). Line segments that are parallel to each other or on the same straight line are wound on the same core and pass the same magnetic flux, so they are in phase.

[0046] In this example, the multi-phase transformer 1 is a 12-phase transformer. On the primary side, each terminal of the star-connected three-phase winding is connected to each line R0, S0, and T0 of the three-phase AC of the system power. The neutral point of the star connection is grounded. On the secondary side, multiple windings are basically delta-connected. In general, the combination of a primary star connection and a secondary delta connection is often used in step-down transformers. Among the line voltage waveforms in Figure 6(a), the first three-phase AC consisting of V1r, V1s, and V1t is the basic three-phase AC, and the other three-phase AC are derived from the basic three-phase AC.

[0047] FIG. 10(a) is a detailed vector diagram of the secondary winding in FIG. 9. The length of each line segment is the magnitude of the vector, and the side with the black circle is regarded as the arrow side of the vector. Terminals R1, S1, and T1, located at the vertices of the largest equilateral triangle, are called the main terminals. Line voltages V1r, V1s, and V1t, which make up the first three-phase AC with a phase difference of 120 degrees from each other, are the voltages between terminals R1 and S1, between terminals S1 and T1, and between terminals T1 and R1, respectively, and are called the R phase, S phase, and T phase.

[0048] In addition to the main terminals R1, S1, and T1, the following nine sub-terminals are provided. Opposite the main terminal R1 are sub-terminals R3, R2, and R4. Opposite the main terminal S1 are sub-terminals S3, S2, and S4. Opposite the main terminal T1 are sub-terminals T3, T2, and T4.

[0049] In the vector diagram, the three sub-terminals R3, R2, and R4 opposite the main terminal R1 are located on a circle c whose center is the main terminal R1 and whose radius is the line segment R1-S1, and are located at 15 degrees, 30 degrees, and 45 degrees, respectively, from the line segment R1-S1. The vectors pointing from the sub-terminals R3, R2, and R4 to the main terminal R1 correspond to the line voltages V2r, V3r, and V4r shown in Figure 6, respectively.

[0050] Similarly, the vectors directed from the sub-terminals S3, S2, and S4 to the main terminal S1 correspond to the line voltages V2s, V3s, and V4s shown in Fig. 6. The vectors directed from the sub-terminals T3, T2, and T4 to the main terminal T1 correspond to the line voltages V2t, V3t, and V4t shown in Fig. 6.

[0051] A traditional 12-phase transformer can be realized by providing windings corresponding to three lines directly connecting each main terminal and nine lines directly connecting each main terminal and its opposite sub-terminal. In that case, it is necessary to provide three main windings between each main terminal and nine auxiliary windings with the same number of turns as the main windings. If each of the 12 phases is provided with a separate winding like this, there is a problem that the transformer becomes large. In contrast, the present invention provides multiple auxiliary windings with a relatively small number of turns, thereby reducing the number of turns of the entire secondary winding. For example, the auxiliary winding is branched off from the main winding, or the divided main windings are connected by the auxiliary winding. As a result, the transformer can be made smaller in size.

[0052] Here, the "main winding" refers to the winding located on the line segment connecting the main terminals R1, S1, and T1 in the vector diagram, and the "auxiliary winding" refers to the winding located anywhere else.

[0053] In the specific example of Fig. 10(a), the R-phase main winding is divided into two, r1 and r2, the S-phase main winding is divided into two, s1 and s2, and the T-phase main winding is divided into two, t1 and t2. An S-phase auxiliary winding s4 and a T-phase auxiliary winding t3 are connected in series between the two divided R-phase main windings r1 and r2. The connection point between the auxiliary winding s4 and the auxiliary winding t3 is connected to the sub-terminal T2.

[0054] An S-phase auxiliary winding s6 is connected alone between a branch point of the main winding r1 and a sub-terminal T3. The main winding r1 is divided into a partial main winding r11 and a partial main winding r12 at the branch point. A T-phase auxiliary winding t5 is connected alone between a branch point of the main winding r2 and a sub-terminal T4. The main winding r2 is divided into a partial main winding r21 and a partial main winding r22 at the branch point.

[0055] Similarly, a T-phase auxiliary winding t4 and an R-phase auxiliary winding r3 are connected in series between the two S-phase divided main windings s1 and s2. The connection point between the auxiliary windings t4 and r3 is connected to the sub-terminal R2.

[0056] A T-phase auxiliary winding t6 is connected alone between a branch point of the main winding s1 and a sub-terminal R3. The main winding s1 is divided into a partial main winding s11 and a partial main winding s12 at the branch point. An R-phase auxiliary winding r5 is connected alone between a branch point of the main winding s2 and a sub-terminal R4. The main winding s2 is divided into a partial main winding s21 and a partial main winding s22 at the branch point.

[0057] Similarly, an R-phase auxiliary winding r4 and an S-phase auxiliary winding s3 are connected in series between the two T-phase divided main windings t1 and t2. The connection point between the auxiliary windings r4 and s3 is connected to the sub-terminal S2.

[0058] An R-phase auxiliary winding r6 is connected alone between a branch point of the main winding t1 and a sub-terminal S3. The main winding t1 is divided into a partial main winding t11 and a partial main winding t12 at the branch point. An S-phase auxiliary winding s5 is connected alone between a branch point of the main winding t2 and a sub-terminal S4. The main winding t2 is divided into a partial main winding t21 and a partial main winding t22 at the branch point.

[0059] Here, the multiple main windings and multiple auxiliary windings included in each of the three winding groups arranged between main terminals R1 and S1, between main terminals S1 and T1, and between main terminals T1 and R1, respectively, are consistent in terms of relative phase relationships, relative numbers of turns, and connection relationships between the windings. For example, the phase relationship between the main winding r1 and the auxiliary winding s4 matches that between the main winding s1 and the auxiliary winding t4, and matches that between the main winding t1 and the auxiliary winding r4. For example, the partial main windings r11, s11, and t11 have the same number of turns, and the partial main windings r12, s12, and t12 have the same number of turns. For example, the connection relationship between the auxiliary windings s4 and t3, the connection relationship between the auxiliary windings t4 and r3, and the connection relationship between the auxiliary windings r4 and s3 match.

[0060] In other words, the three windings that are in corresponding positions with respect to the three sides of the equilateral triangle in the vector diagram are 120 degrees out of phase with each other and have the same number of turns. The combinations of such three windings are as follows: ·Main windings r1, s1 and t1 ·Main windings r2, s2 and t2 Partial main windings r11, s11 and t11 Partial main windings r12, s12 and t12 Partial main windings r21, s21 and t21 Partial main windings r22, s22 and t22 Auxiliary windings r3, s3 and t3 Auxiliary windings r4, s4 and t4 Auxiliary windings r5, s5 and t5 Auxiliary windings r6, s6 and t6 This configuration provides the advantage that output current is evenly distributed from each phase, resulting in good phase balance.

[0061] The irregular delta connection as described above can reduce the secondary winding of the 12-phase transformer as a whole, and can make the transformer smaller. For example, the line voltage Vr2, which is 15 degrees out of phase with the line voltage Vr1, corresponds to a vector that points from the sub-terminal R3 to the main terminal R1. This one vector is the same as a combination of the vectors of the auxiliary winding t6, the partial main winding s11, the main winding r2, the auxiliary winding t3, the auxiliary winding t4, and the main winding r1. In other words, instead of providing one winding that directly connects the sub-terminal R3 and the main terminal R1 to generate the line voltage Vr2, the auxiliary winding t6, the partial main winding s11, the main winding r2, the auxiliary winding t3, the auxiliary winding t4, and the main winding r1 are used. In this case, the windings other than the auxiliary winding t6 are also used to generate other line voltages, and are therefore used for both purposes. This can reduce the windings as a whole.

[0062] Another characteristic feature is a V-shaped connection in which the main winding r1 and the main winding r2, which are separated from each other, are connected by the auxiliary winding s4 and the auxiliary winding t3, and the connection point of the auxiliary winding s4 and the auxiliary winding t3 is connected to the sub-terminal T2. A similar V-shaped connection is also formed in each of the sub-terminals R2 and S2. In this way, the portion where one end of two auxiliary windings with the same number of turns of two phases with a phase difference of 120 degrees are connected to each other is referred to as a "V-connection portion." With this configuration, current is supplied from two windings to the sub-terminals T2, R2, and S2, which has the effect of increasing the output current and reducing the impedance. The V-connection portion is provided in at least one sub-terminal of each phase.

[0063] The table in Fig. 10(b) shows an example of the line voltages of the first three-phase AC between each main terminal and the phase voltages of each winding in Fig. 10(a). The number of turns of each winding is proportional to the value of each phase voltage.

[0064] Figure 11 is a winding connection diagram of a 12-phase transformer based on the vector diagram of Figure 10(a). The primary side R-phase winding and secondary side R-phase windings r1 to r6 are wound on the same core, the primary side S-phase winding and secondary side S-phase windings s1 to s6 are wound on the same core, and the primary side T-phase winding and secondary side T-phase windings t1 to t6 are wound on the same core. The phase voltages of the windings wound on the same core have the same phase.

[0065] 12(a) to (j) show variations of the secondary side connections of the 12-phase transformer shown in FIG. 10(a). As described above, the main windings and auxiliary windings included in each of the three winding groups arranged between the main terminals R1 and S1, between the main terminals S1 and T1, and between the main terminals T1 and R1, respectively, are consistent in terms of relative phase relationship, relative number of turns, and connection relationship between the windings. As long as this condition is satisfied, various modifications are possible. The examples shown in FIG. 12 are some of the various modifications.

[0066] In Figures 12(a), (b), and (c), the phases of the auxiliary windings connected to the sub-terminals R3, R4, S3, S4, T3, and T4 are changed. In Figure 12(d) and (e), the position of the V-connection part is changed. The number of turns of the two main windings of each phase is different, and two auxiliary windings branch off from two branch points of one main winding and connect to two sub-terminals, while the other main winding has no branch points. In Figure 12(f), (g), and (h), two V-connections are provided for each phase, and their positions are changed. Each phase has three separated main windings. In Fig. 12(i), three V-connection parts are provided for each phase. There is no separate auxiliary winding. Thus, a V-connection part is provided at at least one sub-terminal of each phase. Figure 12(j) shows an example where no V-connection is provided. In this case, each main winding is a single undivided winding, and the auxiliary windings connected to each sub-terminal are also single windings. This also has the effect of reducing the overall number of windings compared to a general delta-connected multi-phase transformer.

[0067] FIG. 13(a) shows another example of a multi-phase transformer 1. This example is also a 12-phase transformer. On the primary side, each terminal of the delta-connected three-phase winding is connected to each of the three-phase AC lines R0, S0, and T0 of the system power. On the secondary side, multiple windings are basically star-connected. The neutral point is grounded. In general, the combination of a primary delta connection and a secondary star connection is often used in step-up transformers.

[0068] The main windings r1, s1, and t1 are connected to the main terminals R1, S1, and T1. As in the delta connection in FIG. 10(a), sub-terminals R3, R2, and R1 are provided at 15-degree intervals on a circle c whose center is the main terminal R1 and whose radius is the line segment connecting the main terminals R1 and S1. Similarly, sub-terminals S3, S2, and S1 and sub-terminals T3, T2, and T1 are provided. Auxiliary windings r2, s2, and t2 are connected between the neutral point and each of the sub-terminals R2, S2, and T2. One end of the auxiliary windings t3 and s4 is connected to the branch point of the main winding r1, one end of the auxiliary windings r3 and t4 is connected to the branch point of the main winding s1, one end of the auxiliary windings s3 and r4 is connected to the branch point of the main winding t1, and the other end of each is connected to each sub-terminal. In this example as well, the 12-phase line voltages V1r to Vt4 shown in FIG. 6(a) are output from the 12 terminals R1 to T4 on the secondary side.

[0069] The table in Fig. 13(b) shows an example of the line voltages of the first three-phase AC between each main terminal and the phase voltages of each winding in Fig. 13(a). The number of turns of each winding is proportional to the value of each phase voltage.

[0070] FIG. 14(a) is a vector diagram similar to FIG. 10(a) showing another example of secondary side wiring of the multi-phase transformer 1. (b) is a vector diagram of the secondary side line voltage. The multi-phase transformer 1 of this example is a nine-phase transformer. Sub-terminals R2 and R3 are arranged opposite the main terminal R1, sub-terminals S2 and S3 are arranged opposite the main terminal S1, and sub-terminals T2 and T3 are arranged opposite the main terminal T1, so that a total of nine secondary side terminals are provided. In this case, the first three-phase AC Vr1, Vs1, and Vt1, the second three-phase AC Vr2, Vs2, and Vt2 whose phases are delayed by 20 degrees from the first three-phase AC, and the third three-phase AC Vr3, Vs3, and Vt3 whose phases are delayed by 40 degrees from the first three-phase AC are output as line voltages.

[0071] As shown in Fig. 14(a), the sub-terminals R2, T2, and S3 are the V-connection portion described above. The sub-terminals R3, S3, and T3 are independent auxiliary windings that branch off from the main winding. For the 9-phase transformer, there are also variations in the V-connection portion and / or auxiliary winding, similar to the 12-phase transformer shown in Fig. 12. Also for the 9-phase transformer, there is a variation in which there is no V-connection portion, as shown in Fig. 12(j) for the 12-phase transformer.

[0072] The interconnection circuit section connected to the nine-phase transformer is similar to that shown in Figs. 1 to 5, except that the number of secondary terminals of the multi-phase transformer is different.

[0073] FIG. 15(a) is a vector diagram similar to FIG. 10(a) showing yet another example of secondary side wiring of the multi-phase transformer 1. (b) is a vector diagram of the secondary side line voltage. The multi-phase transformer 1 of this example is a six-phase transformer. A sub-terminal R2 is disposed opposite the main terminal R1, a sub-terminal S2 is disposed opposite the main terminal S1, and a sub-terminal T2 is disposed opposite the main terminal T1, so that a total of six secondary side terminals are provided. In this case, the first three-phase AC Vr1, Vs1, and Vt1, and the second three-phase AC Vr2, Vs2, and Vt2, which are 30 degrees behind the first three-phase AC, are output as line voltages.

[0074] As shown in Fig. 15(a), the sub-terminals R2, T2, and S3 form the V-connection portion described above. In the case of a 6-phase transformer, there is also a variation in which there is no V-connection portion as shown in Fig. 12(j) for a 12-phase transformer.

[0075] The interconnection circuit section connected to the six-phase transformer is similar to that shown in Figs. 1 to 5, except that the number of secondary terminals of the multi-phase transformer is different.

[0076] In principle, the multi-phase transformer 1 is not limited to 12-phase, 9-phase, or 6-phase, but includes those that convert three-phase AC to 3n-phase polyphase AC. n is a natural number of 2 or more. When n=4, it is a 12-phase transformer, when n=3, it is a 9-phase transformer, and when n=2, it is a 6-phase transformer. The secondary side terminals consist of first to third main terminals that output the first three-phase AC, and fourth to third sub-terminals. The line voltages on the secondary side are the first three-phase AC Vr1, Vs1, and Vst, and the second to n-th three-phase ACs that are delayed in phase by 60 / n degrees, 2×(60 / n) degrees,..(n-1)×(60 / n) degrees from each phase of the first three-phase AC, respectively.

[0077] As n becomes larger, the pulsation in the full-wave rectified waveform shown in Fig. 6(b) becomes less and closer to DC. However, as n becomes larger, the configuration of the multi-phase transformer and the interconnection circuit becomes more complex and the number of parts increases. As the multi-phase transformer of the present invention, a 12-phase transformer with n=4 is suitable.

[0078] Although the embodiment of the present invention has been described above with reference to exemplary configurations, the specific configurations are not limited to these. As long as the principles of the present invention are followed, various modifications are also included in the scope of the present invention. [Explanation of symbols]

[0079] 1. Polyphase Transformer 10 Grid connection circuit section 11 Positive circuit 12 Negative side circuit 4 Resistance elements 5. Storage battery 6, 7 DC connection terminals P1 First positive rectifier P2 Second positive rectifier N1 First negative rectifier N2 Second negative rectifier SW Switch R0, S0, T0 Three-phase AC lines R1, S1, T1 main terminals R2, R3, R4, S2, S3, S4, T2, T3, T4 sub terminals r1, r2, s1, s2, t1, t2 main winding r11, r12, r21, r22, s11, s12, s21, s22, t11, t12, t21, t22 Partial main winding r3, r4, r5, r6, s3, s4, s5, s6, t3, t4, t5, t6 auxiliary winding V1r, V1s, V1t First three-phase AC (line voltage) V2r, V2s, V2t Second three-phase AC (line voltage) V3r, V3s, V3t Third three-phase AC (line voltage) V4r, V4s, V4t Fourth three-phase AC (line voltage)

Claims

1. A bidirectional power interconnection device that bidirectionally interconnects an AC power section and a DC power section, a multi-phase transformer for converting the three-phase AC power from the AC power unit into a multi-phase AC power of 3n phases (n is a natural number of 2 or more); a first full-wave rectification unit including a plurality of first rectification elements capable of full-wave rectifying the multi-phase AC on the secondary side of the multi-phase transformer and outputting the full-wave rectified AC to the DC power unit; a second full-wave rectification unit including a plurality of second rectification elements capable of full-wave rectifying the multi-phase AC current on the secondary side of the multi-phase transformer and outputting the full-wave rectified AC current to a resistance element; a switch section including a plurality of switch elements respectively in parallel with the plurality of first rectifying elements, each switch element being associated with a respective one of the plurality of second rectifying elements, and configured such that when the associated second rectifying element is non-conductive, the associated switch element is off, and when the associated second rectifying element is conductive, a drive signal for driving the associated switch element is output, thereby switching the associated switch element to on.

2. The plurality of first rectifying elements of the first full-wave rectifying unit include 3n first positive-side rectifying elements each having an anode connected to each secondary-side terminal of the multi-phase transformer and a cathode commonly connected to a positive terminal of the DC power unit; a first negative-side rectifier element having a cathode connected to each of the secondary terminals of the multi-phase transformer and an anode commonly connected to a negative terminal of the DC power unit; The plurality of second rectifying elements of the second full-wave rectifying unit include 3n second positive-side rectifying elements, each having an anode connected to each secondary-side terminal of the multi-phase transformer and a cathode commonly connected to one end of the resistor element; and 3n second negative side rectifying elements, each having a cathode connected to each secondary side terminal of the multi-phase transformer and an anode commonly connected to the other end of the resistive element.

3. A drive unit that switches the switch element on and off includes: a light-emitting element that is connected in series with the second rectifying element and emits light only when the second rectifying element is conductive, and a light-receiving element that receives light from the light-emitting element, 3. The bidirectional power interconnection device according to claim 2, wherein the light receiving element outputs a drive signal that turns the switch element on when light is received from the light emitting element and turns the switch element off when light is not received.

4. the first rectifying element is a parasitic diode of a field effect transistor or a diode connected in parallel with the parasitic diode, 4. The bidirectional power interconnection device according to claim 3, wherein the switch element is a current path between the drain and source of the field effect transistor, and the gate of the field effect transistor is driven by a drive signal from the drive section.

5. the multi-phase transformer has first to third main terminals and fourth to 3n sub-terminals as secondary side terminals, and outputs, as line voltages between predetermined secondary side terminals, a first three-phase AC and second to n-th three-phase ACs each delayed in phase by 60 / n degrees, 2×(60 / n) degrees, . . . (n-1)×(60 / n) degrees from each phase of the first three-phase AC, two or more main windings separated from each other are connected between the first and second main terminals, the second and third main terminals, and the third and first main terminals, respectively, for generating the first three-phase AC; Between the two main windings of one phase that are separated, two auxiliary windings of the other two phases are V-connected, and a connection point between the two auxiliary windings is connected to one of the sub-terminals; 5. The bidirectional power interconnection device according to any one of claims 1 to 4, wherein a plurality of main windings and a plurality of auxiliary windings included in each of the three winding groups respectively arranged between the first and second main terminals, between the second and third main terminals, and between the third and first main terminals are consistent in relative phase relationship, relative number of turns, and connection relationship between the windings.

6. the multi-phase transformer has first to third main terminals and fourth to 3n sub-terminals as secondary side terminals, and outputs, as line voltages between predetermined secondary side terminals, a first three-phase AC and second to n-th three-phase ACs each delayed in phase by 60 / n degrees, 2×(60 / n) degrees, . . . (n-1)×(60 / n) degrees from each phase of the first three-phase AC, two or more main windings separated from each other are connected between the first and second main terminals, the second and third main terminals, and the third and first main terminals, respectively, for generating the first three-phase AC; Between the two main windings of one phase that are separated, two auxiliary windings of the other two phases are V-connected, and a connection point between the two auxiliary windings is connected to one of the sub-terminals; A single auxiliary winding of any of the other two phases is connected between one or more branch points of the main winding of one phase and one or more of the sub-terminals; 5. The bidirectional power interconnection device according to any one of claims 1 to 4, wherein a plurality of main windings and a plurality of auxiliary windings included in each of the three winding groups respectively arranged between the first and second main terminals, between the second and third main terminals, and between the third and first main terminals are consistent in relative phase relationship, relative number of turns, and connection relationship between the windings.

7. the multi-phase transformer has first to third main terminals and fourth to 3n sub-terminals as secondary side terminals, and outputs, as line voltages between predetermined secondary side terminals, a first three-phase AC and second to n-th three-phase ACs each delayed in phase by 60 / n degrees, 2×(60 / n) degrees, . . . (n-1)×(60 / n) degrees from each phase of the first three-phase AC, a main winding is connected between the first and second main terminals, the second and third main terminals, and the third and first main terminals for generating the first three-phase AC; A single auxiliary winding of any of the other two phases is connected between one or more branch points of the main winding of one phase and one or more of the sub-terminals; 5. The bidirectional power interconnection device according to any one of claims 1 to 4, wherein the main winding and one or more auxiliary windings included in each of the three winding groups respectively arranged between the first and second main terminals, between the second and third main terminals, and between the third and first main terminals are consistent in relative phase relationship, relative number of turns, and connection relationship between the windings.

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