DC power supply device

Abstract

To suppress cyclic current at a DC side of a DC power supply having two rectification circuits to which three-phase AC power supply is inputted.SOLUTION: At a primary side of a first power transformer 3 and a second power transformer 4 whose phase shift angle difference is 30°, a main winding and a phase shift winding are star-connected between a three-phase AC power supply and a primary side neutral Np in a manner that current flows through the first power transformer 3 and the second power transformer 4 in series at each of UVW phases. At a secondary side of the first power transformer 3, a first rectification element group 31 in which an AC side is connected to a secondary winding of the uvw phases and xyz phases is arranged and at the secondary side of the second power transformer 4, a second rectification element group 32 in which the AC side is connected to the secondary winding of the uvw phases and the xyz phases is arranged. At the first rectification element group 31 and the second rectification element group 32, a DC side of each rectification element in which the AC side is connected to the secondary winding of the uvw phases is mutually connected, and the DC side of each rectification element in which the AC side is connected to the secondary winding of the xyz phases is mutually connected.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a DC power supply device, and more particularly to a DC power supply device having a rectifier circuit that receives a three-phase AC power supply as an input. [Background technology]

[0002] As one form of DC power supply that receives a three-phase AC power supply, a multi-phase configuration is known in which rectifier circuits are combined to suppress harmonics. For example, Non-Patent Document 1 below describes a so-called 12-pulse rectifier circuit that is configured by connecting two rectifier circuits in parallel to which a three-phase AC voltage having a phase difference of 30° is input.

[0003] Furthermore, Non-Patent Document 1 describes a technique for suppressing harmonics in the input current on the power supply side by optimizing an interphase reactor for absorbing the output voltage difference between two rectifier circuits. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Toshihiko Tanaka and Shuji Oshio, "A Method for Reducing Power Supply Harmonic Currents in Parallel-Connected Thyristor Rectifier Circuits by Optimizing Interphase Reactors," IEEJ Transactions on Industrial Applications, Vol. 117, No. 1, pp. 19-25 (1997) Summary of the Invention [Problem to be solved by the invention]

[0005] It is known that a circulating current occurs between the DC side of a 12-pulse rectifier circuit in which two rectifier circuits are connected, as in Non-Patent Document 1. Electromagnetic induction caused by this circulating current may cause induction heating of iron structures near the DC terminals of the rectifier or near the DC conductor between the rectifier circuits.

[0006] In Non-Patent Document 1, it is possible to suppress circulating current by using the inductance of an interphase reactor. Alternatively, in some cases, it is possible to ensure inductance for equivalently suppressing circulating current by lengthening the DC conductor between rectifier circuits without directly arranging a reactor.

[0007] However, there is a concern that the above-mentioned measures to suppress circulating currents will require an increase in the size of the interphase reactor or DC conductor, and that such an increase in size will lead to increased losses.

[0008] The present disclosure has been made to solve such problems, and an object of the present disclosure is to suppress circulating current on the DC side of a DC power supply device configured as a 12-pulse rectifier circuit that receives a three-phase AC power supply as input. [Means for solving the problem]

[0009] A DC power supply device according to an embodiment of the present disclosure includes a first transformer and a second transformer configured such that the difference between the phase angles of the first and second transformers is 30°, a first rectifier element, and a second rectifier element. The first transformer has a first UVW-phase primary winding, a first uvw-phase secondary winding, and a first xyz-phase secondary winding that are star-connected to a secondary neutral point. The second transformer has a second UVW-phase primary winding, and a second uvw-phase secondary winding and a second xyz-phase secondary winding that are star-connected to a secondary neutral point common to the first transformer. The first rectifier element group has AC sides connected to the first uvw-phase secondary winding and the first xyz-phase secondary winding. The second rectifier element has AC sides connected to the second uvw-phase secondary winding and the second xyz-phase secondary winding. At least one of the first and second transformers is configured as a phase-shifting transformer in which the first UVW phase primary winding or the second UVW phase primary winding has a main winding and a phase-shifting winding. On the primary sides of the first and second transformers, the first UVW phase primary winding and the second UVW phase primary winding are star-connected between a three-phase AC power source and a common primary neutral point in a manner in which current flows in series through the first and second transformers in the U, V, and W phases, respectively. On the secondary sides of the first transformer and the second transformer, the DC side of the first rectifier element connected to the first uvw-phase secondary winding and the DC side of the second rectifier element connected to the second uvw-phase secondary winding are interconnected, while the DC side of the first rectifier element connected to the first xyz-phase secondary winding and the DC side of the second rectifier element connected to the second xyz-phase secondary winding are interconnected. Effect of the Invention

[0010] According to the present disclosure, it is possible to suppress circulating current on the DC side of a DC power supply device configured as a 12-pulse rectifier circuit that receives an input from a three-phase AC power supply. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a conceptual diagram illustrating a configuration of a DC power supply device according to a comparative example. [Diagram 2] 1 is a conceptual diagram illustrating a configuration of a DC power supply device according to an embodiment of the present invention. [Diagram 3] FIG. 1 is a circuit diagram showing a configuration example of a DC power supply device according to a comparative example. [Figure 4] 1 is a circuit diagram showing a configuration example of a DC power supply device according to an embodiment of the present invention; [Diagram 5] 4 is a waveform diagram of an output current of a rectifier element of the DC power supply device according to the present embodiment. FIG. [Figure 6] 5 is a current waveform diagram of each phase on the primary side of the transformer in FIG. 4. [Figure 7] 5 is a current waveform diagram of a rectifier element of each phase on the secondary side of the transformer of FIG. 4. [Figure 8] 4 is a waveform diagram showing a simulation result of an output current of a rectifier element of each phase on the secondary side in the DC power supply device (comparative example) shown in FIG. 3. FIG. [Figure 9] 5 is a waveform diagram showing a simulation result of an output current of a rectifier element of each phase on the secondary side in the DC power supply device (present embodiment) shown in FIG. 4. [Figure 10] 4 is a waveform diagram showing a simulation result of an output current of the DC power supply device (comparative example) shown in FIG. 3. FIG. [Figure 11] 5 is a waveform diagram showing a simulation result of an output current of the DC power supply device (the present embodiment) shown in FIG. 4. [Figure 12] 1 is a conceptual waveform diagram of the output current of a rectifier element in each phase on the secondary side of a transformer whose secondary side is double star-connected. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are designated by the same reference characters, and their description will not be repeated in principle.

[0013] (Circuit configuration) First, the circuit configuration of the DC power supply device according to this embodiment will be described by comparing it with a 12-pulse rectifier circuit in which two rectifier circuits, to which a three-phase AC voltage having a phase difference of 30° is input, are connected in parallel, as in Non-Patent Document 1.

[0014] FIG. 1 is a conceptual diagram illustrating the configuration of a DC power supply device according to a comparative example.

[0015] As shown in FIG. 1, a DC power supply device 10 according to the comparative example includes rectifier circuits 21 and 22 connected in parallel, and DC reactors L1 and L2, and supplies DC power to a load (DC load) 40.

[0016] The rectifier circuit 21 includes a transformer 3 having a primary winding group 3P composed of main windings and phase shift windings of each of the UVW phases, a secondary winding group 3S composed of windings of each of the uvw phases and xyz phases, and a first rectifier element group 31. Each rectifier element of the first rectifier element group 31 is formed of, for example, a thyristor, and has an AC side (anode) connected to each of the uvw phases and xyz phases of the secondary winding group 3S, and a DC side (cathode) connected to the DC conductor PL1.

[0017] Similarly, the rectifier circuit 22 includes a transformer 4 having a primary winding group 4P composed of main windings and phase shift windings of each of the UVW phases and a secondary winding group 4S composed of windings of each of the uvw phases and xyz phases, and a second rectifier element group 32. Each rectifier element of the second rectifier element group 32 is formed of, for example, a thyristor, and has an AC side (anode) connected to each of the uvw phases and xyz phases of the secondary winding group 4S, and a DC side (cathode) connected to the DC conductor PL2.

[0018] In this specification, the primary side (UVW phase) of each phase of the transformers 3 and 4 is written in capital letters, and the secondary side (uvw phase, xyz phase) is written in lower case letters. Furthermore, in order to distinguish between the UVW phases on the primary side of the transformers 3 and 4, the U phase, V phase, and W phase on the primary side of the transformer 3 are also referred to as the U1 phase, V1 phase, and W1 phase. On the other hand, the U phase, V phase, and W phase on the primary side of the transformer 4 are also referred to as the U2 phase, V2 phase, and W2 phase. Similarly, in order to distinguish between the uvw phase and the xyz phase on the secondary side of the transformers 3 and 4, each phase on the secondary side of the transformer 3 is also referred to as the u1 phase, v1 phase, w1 phase, and x1 phase, y1 phase, and z1 phase. Similarly, each phase on the secondary side of the transformer 4 is also referred to as the u2 phase, v2 phase, w2 phase, and x2 phase, y2 phase, and z2 phase.

[0019] The main winding and phase shift windings (U1-W1 phase) of the primary winding group 3P of the transformer 3 are star-connected to the primary neutral point Np1 so as to be configured as a transformer with phase shift windings (phase shift transformer) having a phase shift angle of -15°. The secondary winding group 3S of the transformer 3 is star-connected to a common secondary neutral point Ns for the u1, v1, and w1 phases and the x1, y1, and z1 phases. In other words, the u1-w1 phases and the x1-z1 phases are connected in parallel.

[0020] On the other hand, the main winding and phase shift winding (U2 phase to W2 phase) of the primary winding group 4P of the transformer 4 are star-connected to the primary neutral point Np2 so as to be configured as a transformer with phase shift windings (phase shift transformer) having a phase shift angle of +15°. The secondary winding group 4S is star-connected to the secondary neutral point Ns shared with the transformer 3 in each of the uvw phases (u2 phase to w2 phase) and the xyz phases (x2 phase to z2 phase), similar to the secondary winding group 3S. That is, the u2 phase to w2 phase and the x2 phase to z2 phase are also connected in parallel.

[0021] A primary winding group 3P of the transformer 3 and a primary winding group 4P of the transformer 4 are connected in parallel to a three-phase AC power supply (not shown) via power lines PLU, PLV, and PLW.

[0022] A first terminal of the load 40 is connected to the DC conductors PL1 and PL2, and a second terminal is connected to the secondary neutral point Ns of the commonly connected transformers 3 and 4.

[0023] The rectifier circuits 21 and 22 are connected in parallel to a three-phase AC power supply by power lines PLU to PLW, and the 12 rectifier elements constituting the first rectifier element group 31 and the second rectifier element group 32 operate to rectify AC voltages with a phase difference of 30° each, thereby achieving operation as a 12-pulse rectifier circuit.

[0024] The DC reactors L1, L2 can also be configured by the inductance of the DC conductors PL1, PL2, and have the effect of suppressing the circulating current circulating between the DC conductors PL1 and PL2, similar to the interphase reactor of Non-Patent Document 1.

[0025] FIG. 2 shows a conceptual diagram illustrating the configuration of a DC power supply device according to this embodiment.

[0026] Referring to FIG. 2, a DC power supply device 11 according to this embodiment is similar to a DC power supply device 10 (FIG. 1) according to the comparative example in that, while the components of rectifier circuits 21 and 22 are similar, the connections of primary winding groups 3P, 4P on the primary side of transformers 3 and 4 and the DC side connections of first rectifier group 31 and second rectifier group 32 on the secondary side are different.

[0027] Specifically, on the primary sides of the transformers 3 and 4, the main winding and phase shift winding (U1 phase to W1 phase) of the primary winding group 3P and the main winding and phase shift winding (U2 phase to W2 phase) of the primary winding group 4P are star-connected between the power lines PLU to PLV (three-phase AC power source) and a primary side neutral point Np common to the transformers 3 and 4 so that the currents of the UVW phases on the primary side flow in series rather than in parallel through the primary winding groups 3P and 4P. A specific example of the connection of the primary winding groups 3P and 4P will be described later using a circuit diagram.

[0028] On the secondary side of the transformers 3, 4, the first rectifier element group 31 and the second rectifier element group 32 do not operate in parallel as in Fig. 1, but the DC sides of the rectifier elements are interconnected for uvw phases and xyz phases, so that they operate as one unit. In the example of Fig. 2, the DC conductor PL1 is connected to the DC sides of the rectifier elements constituting the first rectifier element group 31 and the second rectifier element group 32, whose AC sides are connected to the uvw phases (u1 phase to w1 phase, u2 phase to w2 phase) of the transformers 3, 4. The DC conductor PL2 is connected to the DC sides of the rectifier elements constituting the first rectifier element group 31 and the second rectifier element group 32, whose AC sides are connected to the xyz phases (x1 phase to z1 phase, x2 phase to z2 phase) of the transformers 3, 4.

[0029] In this way, the DC power supply 11 according to the present embodiment differs from the DC power supply 10 according to the comparative example in that the phase currents on the primary side of the transformer do not flow in parallel to the transformers 3 and 4, but flow in series through the transformers 3 and 4. As a result, as will be made clear later, the DC power supply 11 is able to significantly reduce circulating current compared to the DC power supply 10 according to the comparative example, and as indicated by the dotted lines in FIG. 2, the DC reactors L1 and L2 can be omitted.

[0030] Next, the differences between the DC power supply device 10 according to the comparative example and the DC power supply device 11 according to the present embodiment will be further described with reference to the circuit diagrams of FIGS. 3 and 4. FIG.

[0031] FIG. 3 is a circuit diagram illustrating a configuration example of the DC power supply device 10 (comparative example) shown in FIG.

[0032] 3, the primary sides of the transformers 3 and 4 are star-connected to separate primary neutral points Np1 and Np2, respectively. The primary winding group 3P of the transformer 3 has primary windings Pu11 and Pw12 constituting the main winding and phase shift winding of the U phase (U1 phase), primary windings Pv11 and Pu12 constituting the main winding and phase shift winding of the V phase (V1 phase), and primary windings Pw11 and Pv12 constituting the main winding and phase shift winding of the W phase (W1 phase), all of which are star-connected to the primary neutral point Np1.

[0033] Similarly, the primary winding group 4P of the transformer 4 has primary windings Pu21 and Pv22 constituting the main winding and phase shift winding of the U phase (U2 phase), primary windings Pv21 and Pw22 constituting the main winding and phase shift winding of the V phase (V2 phase), and primary windings Pw21 and Pu22 constituting the main winding and phase shift winding of the W phase (W2 phase), which are star-connected to the primary side neutral point Np2.

[0034] The symbols for each primary winding are indicated by "P (Primary)", followed by an alphabet (lower case) indicating which phase current flows through it, among the U phase, V phase, and W phase, and then a number indicating whether it is the winding of transformer 3 ("1") or transformer 4 ("2"), and a number indicating whether it is the main winding ("1") or the phase shift winding ("2"), making a total of four digits.

[0035] On the secondary sides of the transformers 3 and 4, the secondary winding groups 3S and 4S are star-connected to a common secondary neutral point Ns. The secondary winding group 3S has uvw-phase secondary windings Su1, Sv1, and Sw1, and xyz-phase secondary windings Sx1, Sy1, and Sz1. Similarly, the secondary winding group 4S has uvw-phase secondary windings Su2, Sv2, and Sw2, and xyz-phase secondary windings Sx2, Sy2, and Sz2.

[0036] In the transformer 3, a primary winding Pu11 (U1-phase main winding) and a primary winding Pu12 (V1-phase phase shift winding) are connected in series between a power line PLU (U-phase of a three-phase AC power supply) and a primary side neutral point Np1 so as to make the phase shift angle negative. Furthermore, a primary winding Pv11 (V1-phase main winding) and a primary winding Pv12 (W1-phase phase shift winding) are connected in series between a power line PLV (V-phase of a three-phase AC power supply) and a primary side neutral point Np1, and a primary winding Pw11 (W1-phase main winding) and a primary winding Pw12 (U1-phase phase shift winding) are connected in series between a power line PLW (W-phase of a three-phase AC power supply) and a primary side neutral point Np1. Furthermore, in each of the U1 to W1 phases, the turn ratio (N11:N12) between the main winding and the phase shift winding is determined so that the phase shift angle is 15°.

[0037] In the transformer 3, the primary windings Pu11 and Pw12, which are the U1-phase main winding and phase shift winding, are magnetically coupled to the u1-phase secondary winding Su1 and the x1-phase secondary winding Sx1. Also, the primary windings Pv11 and Pu12, which are the V1-phase main winding and phase shift winding, are magnetically coupled to the v1-phase secondary winding Sv1 and the y1-phase secondary winding Sy1. Furthermore, the primary windings Pw11 and Pv12, which are the W1-phase main winding and phase shift winding, are magnetically coupled to the w1-phase secondary winding Sw1 and the z1-phase secondary winding Sz1.

[0038] In each secondary winding, an AC current having an amplitude according to the turns ratio is induced according to the magnetic flux synthesized by the current flowing through the primary windings (main winding and phase shift winding). As a result, the transformer 3 constitutes a phase transformer with a phase shift angle of -15° as shown in Figure 1.

[0039] On the other hand, in the transformer 4, the primary winding Pu21 (U2-phase main winding) and the primary winding Pu22 (W2-phase phase shift winding) are connected in series between the power line PLU (U-phase of the three-phase AC power supply) and the primary neutral point Np2 so that the phase shift angle is positive. Furthermore, the primary winding Pv21 (V2-phase main winding) and the primary winding Pv22 (U2-phase phase shift winding) are connected in series between the power line PLV (V-phase of the three-phase AC power supply) and the primary neutral point Np2, and the primary winding Pw21 (W2-phase main winding) and the primary winding Pw22 (V2-phase phase shift winding) are connected in series between the power line PLW (W-phase of the three-phase AC power supply) and the primary neutral point Np2.

[0040] In the transformer 4, the primary windings Pu21 and Pv22, which are the U2-phase main winding and phase shift winding, are magnetically coupled to the u2-phase secondary winding Su2 and the x2-phase secondary winding Sx2. The primary windings Pv21 and Pw22, which are the V2-phase main winding and phase shift winding, are magnetically coupled to the v2-phase secondary winding Sv2 and the y2-phase secondary winding Sy2. Furthermore, the primary windings Pw21 and Pu22, which are the W2-phase main winding and phase shift winding, are magnetically coupled to the w2-phase secondary winding Sw2 and the z2-phase secondary winding Sz2.

[0041] As in the transformer 3, an AC current having an amplitude according to the turns ratio is induced in each secondary winding according to the magnetic flux synthesized by the current flowing through the primary windings (main winding and phase shift winding). As a result, the transformer 4 constitutes a phase transformer with a phase shift angle of +15° as shown in FIG.

[0042] The first rectifier group 31 arranged on the secondary side of the transformer 3 includes rectifier elements Tu1, Tv1, Tw1, Tx1, Ty1, and Tz1. The rectifier elements Tu1, Tv1, and Tw1 have an AC side (anode) that receives the AC voltage transmitted to the secondary windings Su1, Sv1, and Sw1 with the same polarity, and a DC side (cathode) that is connected to the DC conductor PL1. On the other hand, the rectifier elements Tx1, Ty1, and Tz1 have an AC side (anode) that receives the AC voltage transmitted to the secondary windings Sx1, Sy1, and Sz1 with the opposite polarity, and a DC side (cathode) that is connected to the DC conductor PL1.

[0043] The second rectifier element group 32 arranged on the secondary side of the transformer 4 includes rectifier elements Tu2, Tv2, Tw2, Tx2, Ty2, and Tz2. The rectifier elements Tu2, Tv2, and Tw2 have AC sides (anodes) that receive the AC voltages transmitted to the secondary windings Su2, Sv2, and Sw2 with the same polarity, and DC sides (cathodes) that are connected to the DC conductor PL2. On the other hand, the rectifier elements Tx2, Ty2, and Tz2 have AC sides (anodes) that receive the AC voltages transmitted to the secondary windings Sx2, Sy2, and Sz2 with the opposite polarity, and DC sides (cathodes) that are connected to the DC conductor PL2. In this way, in the first rectifier element group 31 and the second rectifier element group 32, the AC sides of the uvw-phase rectifier elements and the AC sides of the xyz-phase rectifier elements are connected to the secondary windings with the opposite polarity.

[0044] 3, the load 40 is represented as a current source 41, and a simulation analysis, which will be described later, is performed. In the DC power supply device 10, the sum of an output current I1 passing through the DC conductor PL1 and DC reactor L1 from the rectifier circuit 21 (first rectifier element group 31) and an output current I2 passing through the DC conductor PL2 and DC reactor L2 from the rectifier circuit 22 (second rectifier element group 32) becomes the supply current to the load 40. The difference between the instantaneous values ​​of the output currents I1 and I2 becomes the circulating current of the DC conductors PL1 and PL2.

[0045] FIG. 4 shows a circuit diagram illustrating a configuration example of the DC power supply device 11 (this embodiment) shown in FIG.

[0046] 4, on the primary sides of the transformers 3 and 4, the main windings and phase shift windings of the primary winding groups 3P and 4P are star-connected to a primary neutral point Np common to the U-phase, V-phase, and W-phase, respectively. Specifically, the primary windings Pu11, Pu12, Pu21, and Pu22 of the transformers 3 and 4 are connected in series between the power line PLU (U-phase of the three-phase AC power supply) and the primary neutral point Np. Similarly, the primary windings Pv11, Pv22, Pv21, and Pv22 of the transformers 3 and 4 are connected in series between the power line PLV (V-phase of the three-phase AC power supply) and the primary neutral point Np. Furthermore, primary windings Pw11, Pw12, Pw21, and Pw22 of transformers 3 and 4 are connected in series between the power line PLW (W phase of the three-phase AC power supply) and the primary side neutral point Np.

[0047] 4, primary winding group 3P for configuring a phase-shift transformer with a phase-shift angle of -15° and primary winding group 4P for configuring a phase-shift transformer with a phase-shift angle of +15° are connected in series in each of the UVW phases on the primary side of transformers 3 and 4. That is, the sets of main windings and phase-shift windings connected in parallel in Fig. 3 are connected in series between the three-phase AC power source and the primary side neutral point Np, resulting in a star-connected configuration with a single UVW phase.

[0048] The secondary winding groups 3S, 4S of the transformers 3 and 4 are star-connected to a common secondary neutral point Ns, similar to Fig. 2. Furthermore, the connection relationship between the AC sides (anodes) of the rectifying elements constituting the first rectifying element group 31 and the second rectifying element group 32 and the secondary windings of each phase constituting the secondary winding groups 3S, 4S is similar to that in Fig. 3.

[0049] On the other hand, each of the DC conductors PL1 and PL2 is connected to a part of the DC side of the first rectifier element group 31 and the second rectifier element group 32. Specifically, the DC sides (cathodes) of the u-phase (u1-phase, u2-phase) rectifier elements Tu1, Tu2, the v-phase (v1-phase, v2-phase) rectifier elements Tv1, Tv2, and the w-phase (w1-phase, w2-phase) rectifier elements Tw1, Tw2 are interconnected and commonly connected to the DC conductor PL1.

[0050] In contrast, the DC sides (cathodes) of the x-phase (x1 phase, x2 phase) rectifier elements Tx1, Tx2, the y-phase (y1 phase, y2 phase) rectifier elements Ty1, Ty2, and the z-phase (z1 phase, z2 phase) rectifier elements Tz1, Tz2 are interconnected and commonly connected to the DC conductor PL2.

[0051] In this manner, as described above, in the present embodiment 11, the connections of the primary winding groups 3P, 4P on the primary side of the transformers 3 and 4 and the connections between the first rectifier group 31 and the second rectifier group 32 and the DC conductors PL1, PL2 on the secondary side differ from those of the DC power supply device 10 in the comparative example.

[0052] 2 and 4, the primary winding Pu11 corresponds to the "first U-phase main winding", the primary winding Pv11 corresponds to the "first V-phase main winding", and the primary winding Pw11 corresponds to the "first W-phase main winding". The primary winding Pw12 corresponds to the "first U-phase phase-shift winding", the primary winding Pu12 corresponds to the "first V-phase phase-shift winding", and the primary winding Pv12 corresponds to the "first W-phase phase-shift winding". The assembly of the primary windings Pu11, Pv11, Pw11 and the primary windings Pu12, Pv12, Pv12 corresponds to the "first UVW-phase primary winding".

[0053] Similarly, for the primary winding group 4P of the transformer 4, the primary winding Pu21 corresponds to the "second U-phase main winding", the primary winding Pv21 corresponds to the "second V-phase main winding", and the primary winding Pw21 corresponds to the "second W-phase main winding". Furthermore, the primary winding Pv22 corresponds to the "second U-phase phase-shift winding", the primary winding Pw22 corresponds to the "second V-phase phase-shift winding", and the primary winding Pu22 corresponds to the "second W-phase phase-shift winding". And the assembly of the primary windings Pu21, Pv21, Pw21 and the primary windings Pu22, Pv22, Pw22 corresponds to the "second UVW-phase primary winding".

[0054] Similarly, for the secondary winding group 3S of the transformer 3 shown in Figs. 2 and 4, the secondary winding Su1 corresponds to the "first u-phase secondary winding", the secondary winding Sv1 corresponds to the "first v-phase secondary winding", and the secondary winding Sw1 corresponds to the "first w-phase secondary winding". The assembly of the secondary windings Su1, Sv1, and Sw1 corresponds to the "first uvw-phase secondary winding". In addition, the secondary winding Sx1 corresponds to the "first x-phase secondary winding", the secondary winding Sy1 corresponds to the "first y-phase secondary winding", and the secondary winding Sz1 corresponds to the "first z-phase secondary winding". The assembly of the secondary windings Sx1, Sy1, and Sz1 corresponds to the "first xyz-phase secondary winding".

[0055] Furthermore, for the secondary winding group 4S of the transformer 4, the secondary winding Su2 corresponds to the "second u-phase secondary winding", the secondary winding Sv2 corresponds to the "second v-phase secondary winding", the secondary winding Sw2 corresponds to the "second w-phase secondary winding", and the assembly of the secondary windings Su2, Sv2, and Sw2 corresponds to the "second uvw-phase secondary winding". Moreover, the secondary winding Sx2 corresponds to the "2x-phase secondary winding", the secondary winding Sy2 corresponds to the "2y-phase secondary winding", the secondary winding Sz2 corresponds to the "2z-phase secondary winding", and the assembly of the secondary windings Sx2, Sy2, and Sz2 corresponds to the "second xyz-phase secondary winding".

[0056] Moreover, each of the rectifying elements Tu1, Tv1, Tw1, Tx1, Ty1, and Tz1 constituting the first rectifying element group 31 arranged on the secondary side of the transformer 3 corresponds to a "first rectifying element." Similarly, each of the rectifying elements Tu2, Tv2, Tw2, Tx2, Ty2, and Tz2 constituting the second rectifying element group 32 arranged on the secondary side of the transformer 4 corresponds to a "second rectifying element."

[0057] (Theoretical calculation) Next, a theoretical calculation of the operation of the DC power supply device 11 according to this embodiment will be described.

[0058] Here, the U-phase, V-phase, and W-phase currents on the primary side of the integrally connected transformers 3 and 4 are designated as primary side phase currents IU, IV, and IW, respectively.

[0059] Furthermore, on the secondary side of the transformers 3, 4, the u1-phase and x1-phase currents in the first rectifier element group 31 are designated as secondary side phase current Iux1, the v1-phase and y1-phase currents are designated as secondary side phase current Ivy1, and the w1-phase and z1-phase currents are designated as secondary side phase current Iwz1. Similarly, in the second rectifier element group 32, the u2-phase and x2-phase currents are designated as secondary side phase current Iux2, the v2-phase and y2-phase currents are designated as secondary side phase current Ivy2, and the w2-phase and z2-phase currents are designated as secondary side phase current Iwz2.

[0060] If the number of turns of the main winding of each phase on the primary side of transformers 3 and 4 is N11 and the number of turns of the phase shift winding is N12, and the number of turns of the secondary winding is n2, the relationship between each of the above-mentioned primary side phase currents and each of the secondary side phase currents is expressed by the following equations (1) to (6).

[0061] N11·IU-N12·IW=n2·Iux1 …(1) N11·IV-N12·IU=n2·Ivy1 …(2) N11·IW-N12·IV=n2·Iwz1 …(3) N11·IU-N12·IV=n2·Iux2 …(4) N11·IV-N12·IW=n2·Ivy2 …(5) N11·IW-N12·IU=n2·Iwz2 …(6) For each of the secondary side phase currents Iux1, Ivy1, Iwz1, Iux2, Ivy2, and Iwz2 in the above equations (1) to (6), a positive value indicates a phase current of the u phase (u1 phase, u2 phase), v phase (v1 phase, v2 phase), or w phase (w1 phase, w2 phase), and a negative value indicates a phase current of the x phase (x1 phase, x2 phase), y phase (y1 phase, y2 phase), or z phase (z1 phase, z2 phase).

[0062] From equations (1) to (6), the primary side phase currents IU, IV, and IW are expressed by the following equations (7) to (9) using the constant n*=(N12 / N11).

[0063] IU=(Iux1+Iux2-n*·(Ivy1+Iwx2)) / 2 …(7) IV=(Ivy1+Ivy2-n*·(Iwz1+Iux2)) / 2 …(8) IW=(Iwz1+Iwz2-n*·(Iux1+Ivy2)) / 2 …(9) However, in order to simplify the analysis in deriving equations (7) to (9), it is assumed that n2 = (3 / 2) · N11 and N11 / sin45° = N12 / sin15°, so that the following equation (10) holds.

[0064] n2 N11 / (N11 2 +N11·N12+N12 2 )=1 …(10) FIG. 5 shows a waveform diagram of the output current of each rectifier element arranged on the secondary side of transformers 3 and 4 of DC power supply device 11 according to this embodiment, that is, the phase current on the secondary side.

[0065] As shown in FIG. 5, the secondary side current of each phase is a stepped rectangular wave with a current flow period of 150° because the primary sides of the transformers 3 and 4 are connected in series.

[0066] In FIG. 5, it is assumed that a current of 2 [pu] flows through the load 40 (current source 41), and a current of 1 [pu] flows through each of the DC conductors PL1 and PL2.

[0067] In contrast, in the DC power supply device 10 according to the comparative example, it is understood that each phase current on the secondary side is a rectangular wave with a current-carrying period of 120°, similar to a known 12-pulse rectifier circuit. Due to such a change in the phase current waveform on the secondary side, the following effects can be obtained with respect to the circulating current.

[0068] First, by substituting the phase current (secondary side) waveforms in FIG. 5 into equations (7) to (9), the phase currents on the primary side are as shown in FIG.

[0069] As shown in FIG. 6, the primary phase currents IU, IV, and IW of the series-connected transformers 3 and 4 are stepped AC currents that are shifted in phase by 120° each.

[0070] Furthermore, when the primary side phase currents IU, IV, and IW in Fig. 6 are substituted into the formulas (1) to (6), the phase currents on the secondary side of the transformers 3 and 4, i.e., the output currents (DC side) Iu1, Iv1, Iw1, Ix1, Iy1, Iz1, Iu2, Iv2, Iw2, Ix2, Iy2, and Iz2 of the rectifier elements Tu1, Tv1, Tw1, Tx1, Ty1, and Tz1 and the rectifier elements Tu2, Tv2, Tw2, Tx2, Ty2, and Tz2, are as shown in Fig. 7. It can be seen from the waveforms shown in Fig. 7 that on the secondary side of the transformers 3 and 4, five phases are simultaneously energized in each phase section at intervals of 30°.

[0071] The output current Iuvw flowing through the DC conductor PL1 and the output current Ixyz flowing through the DC conductor PL2 are expressed by the following equations (11) and (12) using the secondary phase currents (u1 phase to w1 phase, x1 phase to z1 phase, u2 phase to w2 phase, x2 phase to z2 phase) of the transformers 3 and 4.

[0072] Iuvw=Iu1+Iv1+Iw1+Iu2+Iv2+Iw2 …(11) Ixyz=Ix1+Iy1+Iz1+Ix2+Iy2+Iz2 …(12) 7 into equations (11) and (12), the difference between the output currents Iuvw and Ixyz in each phase section at intervals of 30° can be made 0. Therefore, theoretical calculations reveal that the DC power supply device 11 according to this embodiment can significantly suppress the circulating current.

[0073] The three-stage current values ​​in the secondary phase current waveform can be calculated by substituting these current values ​​as variables into equations (1) to (9) and then solving Iuvw=Ixyz=1.0 in equations (11) and (12). Specifically, the three-stage current values ​​can be calculated as (4-2√3) [pu], (2√3-3) [pu], and (2-√3) [pu], respectively.

[0074] (Simulation analysis results) Next, the results of simulation analysis of the circuits shown in FIGS. 3 and 4 will be described.

[0075] In the simulation analysis, constant current control is simulated by using a current source 41 as a load 40. In addition, in each of Fig. 3 and Fig. 4, the current behavior is simulated with common DC reactors (inductance components) L1 and L2 connected.

[0076] The simulation conditions were a three-phase AC power frequency f=60[Hz], a primary voltage Ep=77[kV] of the transformers 3 and 4, and a secondary voltage Es=256[V]. As circuit constants of the transformers 3 and 4, the percent impedances were %IX=9.60% (reactance component) and %IR=0.90% (resistance component). Furthermore, the inductance of each of the DC reactors L1 and L2 was 1[μH], and each of the output currents I1, I2, Iuvw, and Ixyz was 30[kA] (i.e., the current source 41 was 60[kA]). Also, the control angle α of each rectifier element (thyristor) was 30°.

[0077] FIG. 8 shows waveform diagrams illustrating simulation results of output currents of rectifier elements of each phase on the secondary side of the circuit shown in FIG. 3, that is, the DC power supply device 10 of the comparative example.

[0078] As shown in Figure 8, each phase current on the secondary side has a waveform in which oscillatory components (ripples) due to DC reactors L1 and L2 are superimposed on a rectangular current waveform in a known 12-pulse rectifier circuit, with a current flow period of 5.55 ms corresponding to one cycle of a frequency of 60 Hz being 16.64 ms, or in other words, a conduction angle of 120°.

[0079] Furthermore, in the simulated current waveform in FIG. 8, the average value was 5.00 [kA] and the effective value was 8.68 [kA].

[0080] In contrast, FIG. 9 shows waveform diagrams illustrating simulation results of output currents of rectifier elements of each phase on the secondary side in the circuit shown in FIG. 4, that is, in DC power supply device 11 according to this embodiment.

[0081] As shown in Fig. 9, the current flow period of each phase on the secondary side is 6.94 [ms], i.e., it corresponds to a conduction angle of 150°, and it can be seen that the output current waveform of each phase assumed in Fig. 5 matches well with the simulation results. In the simulated current waveform in Fig. 9, the average value is 5.00 [kA] and the effective value is 8.00 [kA].

[0082] 8 and 9, the average value of the output current is equivalent, so the DC power supply 11 (FIG. 4) according to this embodiment can supply the same power to the load as the DC power supply 10 (FIG. 3) according to the comparative example, i.e., a normal 12-pulse rectifier circuit. Furthermore, a comparison of the effective values ​​of the output current shows that the present embodiment is expected to reduce power loss more than the comparative example.

[0083] FIG. 10 shows the simulation results of output currents I1 and I2 generated in DC conductors PL1 and PL2, which are represented by the sums of the phase currents corresponding to FIG. 8 in the first rectifier element group 31 and the second rectifier element group 32, respectively.

[0084] Specifically, in Fig. 10, similar to Fig. 8 and Fig. 9, the waveforms of the output currents I1 and I2 are shown for a period of 16.64 [ms], which corresponds to one cycle of a frequency of 60 [Hz]. The instantaneous value of the circulating current Icr is represented by the difference between the instantaneous values ​​of the output currents I1 and I2. In the simulation result of Fig. 10, the circulating current Icr is an AC current with an amplitude of 14.11 [kA].

[0085] In contrast to this, FIG. 11 shows the simulation results of output currents Iuvw and Ixyz generated in DC conductors PL1 and PL2, which are respectively expressed as sums of the phase currents corresponding to FIG. 9 according to equations (11) and (12).

[0086] Specifically, Fig. 11(a) shows waveforms of output currents Iuvw and Ixyz in a period of 16.64 [ms], which corresponds to one cycle of a frequency of 60 [Hz], as in Figs. 8 to 10. The instantaneous value of circulating current Icr is represented by the difference between the instantaneous values ​​of output currents Iuvw and Ixyz. It can be seen from Fig. 11(a) that in the simulation results of DC power supply device 11 according to this embodiment, the difference between output currents Iuvw and Ixyz is small, and the circulating current is significantly suppressed.

[0087] Fig. 11(b) shows an enlarged waveform diagram of the dotted frame in Fig. 11(a). In the simulation results of Fig. 11(a) and (b), the circulating current Icr became an AC current with an amplitude of 111 [A].

[0088] In the above theoretical calculation, the transformers 3 and 4 are assumed to be ideal transformers, whereas in the simulation analysis described in Figures 8 to 11, impedance exists in the transformers 3 and 4, so the circulating current Icr is not completely zero in Figures 11(a) and (b). However, a comparison between Figures 10 and 11(b) shows that the circulating current Icr is significantly suppressed (here, reduced by 99.2% in terms of amplitude ratio).

[0089] In this way, in the power supply device according to this embodiment, a difference of 30° is provided in the phase shift angle between the transformers 3, 4 on the primary sides of the transformers 3, 4, and the primary windings (main winding and phase shift winding) are connected in series between the three-phase DC power source and the common primary side neutral point in a star connection, so that the output current from each rectifier element on the secondary side can be made into a stepped waveform with a current conduction period of 150°. Furthermore, by connecting the DC sides of the rectifier elements on the secondary side not for each transformer 3, 4, but for each UVW phase and XYZ phase that integrates the transformers 3, 4, the circulating current can be significantly suppressed.

[0090] In this embodiment, the transformers 3 and 4 are configured by combining a phase-shift transformer with a phase-shift angle of -15° and a phase-shift transformer with a phase-shift angle of +15°, but the design of the phase-shift angles is not limited to this example. For example, when both transformers 3 and 4 are configured by phase-shift transformers, the combination of the phase-shift angles of the two can be other than the combination of -15° and +15° shown as an example, and the difference between the phase-shift angles can be 30°.

[0091] Alternatively, one of the transformers 3 and 4 may be configured as a transformer in which the UVW-phase primary winding is composed of only a main winding without a phase-shift winding, that is, a phase-shift angle is 0°. In this case, the secondary side of the one transformer (phase-shift angle 0°) can be connected as a known double star circuit to provide the UVW phases and the xyz phases. By connecting the secondary side in a double star configuration, it is possible to obtain output currents Iu, Ix, Iv, Iv, Iy, Iw, and Iz of the rectifier elements of the UVW phases and the xyz phases of the secondary side for the currents IU, IV, and IW of the primary side of the UVW phases, which are shifted in phase by 120°, as shown in FIG. 12.

[0092] In this way, when the phase shift angle of one transformer is set to 0°, the turn ratio of the main winding and phase shift winding of the UVW phase primary winding is adjusted so that the other of transformers 3 and 4 is configured as a phase shift transformer with a phase shift angle of +30° or -30°. Furthermore, on the primary sides of transformers 3 and 4, the main winding of one transformer (phase shift angle 0°) and the main winding and phase shift winding of the other transformer (phase shift angle 30° or -30°) are star-connected in series for each of the U phase, V phase, and W phase.

[0093] However, from the viewpoint of manufacturing, it is preferable to construct transformers 3 and 4 using phase-shift transformers with phase shift angles of +15° and -15° as exemplified in this embodiment, since this simplifies the transformer structure and the winding process.

[0094] Moreover, any semiconductor element can be used for each rectifier element constituting the first rectifier element group 31 and the second rectifier element group, as long as it has the function of rectifying the AC voltage of each secondary winding into a DC voltage. For example, each rectifier element constituting the first rectifier element group 31 and the second rectifier element group 32 can be formed using a diode instead of a thyristor. However, when a thyristor is used as in the example of this embodiment, output control becomes possible by controlling the phase (control angle) of the conduction angle.

[0095] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0096] 3,4 Transformer, 3P,4P Primary winding group, 3S,4S Secondary winding group, 10,11 DC power supply, 21,22 Rectifier circuit, 31 1st rectifier group, 32 2nd rectifier group, 40 Load, 41 Current source, I1,I2,Iuvw,Ixyz Output current, Icr Circulating current, Iu,Iv,Iw Primary phase current, Iux1,Iux2,Ivy1,Ivy2,Iwx1,Iwx2,Iwz1,Iwz2 Secondary phase current, L1,L2 DC reactor, Np,Np1,Np2 Primary neutral point, Ns Secondary neutral point, PL1,PL2 DC conductor, PLU,PLV,PLW Power line (three-phase AC power supply), Pu11, Pu12, Pu21, Pu22, Pv11, Pv12, Pv21, Pv22, Pw11, Pw12, Pw21, Pw22 primary windings, Su1, Su2, Sv1, Sv2, Sw1, Sw2, Sx1, Sx2, Sy1, Sy2, Sz1, Sz2 secondary windings, Tu1, Tu2, Tv1, Tv2, Tw1, Tw2, Tx1, Tx2, Ty1, Ty2, Tz1, Tz2 rectifier elements.

Claims

1. 1. A DC power supply device, comprising: The first transformer and the second transformer are configured so that the difference between the phase shift angles of the first transformer and the second transformer is 30°, the first transformer has a first UVW-phase primary winding, and a first uvw-phase secondary winding and a first xyz-phase secondary winding star-connected with respect to a secondary side neutral point; the second transformer has a second UVW-phase primary winding, and a second uvw-phase secondary winding and a second xyz-phase secondary winding star-connected with respect to the secondary side neutral point common to the first transformer, The DC power supply device is a first rectifier element having an AC side connected to each of the first uvw-phase secondary winding and the first xyz-phase secondary winding; a second rectifier element connected at its AC side to each of the second uvw-phase secondary winding and the second xyz-phase secondary winding, At least one of the first transformer and the second transformer is a phase-shifting transformer in which the first UVW-phase primary winding or the second UVW-phase primary winding has a main winding and a phase-shifting winding, On the primary sides of the first transformer and the second transformer, the first UVW-phase primary winding and the second UVW-phase primary winding are star-connected between a three-phase AC power source and a common primary side neutral point in a manner in which current flows in series through the first transformer and the second transformer in U phase, V phase, and W phase, respectively; a DC power supply device, wherein, on the secondary sides of the first transformer and the second transformer, a DC side of the first rectifier element connected to the first uvw-phase secondary winding and a DC side of the second rectifier element connected to the second uvw-phase secondary winding are interconnected, while a DC side of the first rectifier element connected to the first xyz-phase secondary winding and a DC side of the second rectifier element connected to the second xyz-phase secondary winding are interconnected.

2. a DC side of the first rectifier element connected to the first uvw-phase secondary winding and a DC side of the second rectifier element connected to the second uvw-phase secondary winding are commonly connected to a first DC conductor connected to a first end of a DC load, a DC side of the first rectifier element connected to the first x-y-z-phase secondary winding and a DC side of the second rectifier element connected to the second x-y-z-phase secondary winding are commonly connected to a second DC conductor connected to the first end of the DC load, 2. The DC power supply device according to claim 1, wherein a second end of the DC load is connected to the secondary side neutral point.

3. the first UVW-phase primary winding has a main winding and a phase-shift winding connected such that the first transformer is configured as a phase-shift transformer having a phase shift angle of minus 15 degrees; 3. The DC power supply device according to claim 1, wherein the second UVW-phase primary winding has a main winding and a phase-shift winding connected such that the second transformer is configured as a phase-shift transformer having a phase shift angle of plus 15°.

4. the first UVW-phase primary winding includes a first U-phase main winding, a first U-phase phase shift winding, a first V-phase main winding, a first V-phase phase shift winding, a first W-phase main winding, and a first W-phase phase shift winding; the second UVW-phase primary winding includes a second U-phase main winding, a second U-phase phase shift winding, a second V-phase main winding, a second V-phase phase shift winding, a second W-phase main winding, and a second W-phase phase shift winding; the first U-phase main winding, the second U-phase main winding, the first V-phase phase shift winding, and the second W-phase phase shift winding are electrically connected in series between a U-phase of the three-phase AC power supply and the primary side neutral point; the first V-phase main winding, the second V-phase main winding, the first W-phase phase shift winding, and the second U-phase phase shift winding are electrically connected in series between a V-phase of the three-phase AC power supply and the primary side neutral point; 4. The DC power supply device according to claim 3, wherein the first W-phase main winding, the second W-phase main winding, the first U-phase phase shift winding, and the second V-phase phase shift winding are electrically connected in series between a W-phase of the three-phase AC power supply and the primary side neutral point.

5. the first uvw-phase secondary winding includes a first u-phase secondary winding, a first v-phase secondary winding, and a first w-phase secondary winding; the first x-y-z-phase secondary winding includes a first x-phase secondary winding, a first y-phase secondary winding, and a first z-phase secondary winding; the second uvw-phase secondary winding includes a second u-phase secondary winding, a second v-phase secondary winding, and a second w-phase secondary winding; the second x-y-z-phase secondary winding includes a second x-phase secondary winding, a second y-phase secondary winding, and a second z-phase secondary winding; the first U-phase main winding and the first U-phase phase shift winding are magnetically coupled to the first u-phase secondary winding and the first x-phase secondary winding; the first V-phase main winding and the first V-phase phase shift winding are magnetically coupled to the first v-phase secondary winding and the first y-phase secondary winding; the first W-phase main winding and the first W-phase phase shift winding are magnetically coupled to the first w-phase secondary winding and the first z-phase secondary winding; the second U-phase main winding and the second U-phase phase shift winding are magnetically coupled to the second u-phase secondary winding and the second x-phase secondary winding; the second V-phase main winding and the second V-phase phase shift winding are magnetically coupled to the second v-phase secondary winding and the second y-phase secondary winding; the second W-phase main winding and the second W-phase phase shift winding are magnetically coupled to the second w-phase secondary winding and the second z-phase secondary winding; each of the first u-phase secondary winding, the first v-phase secondary winding, the first w-phase secondary winding, the second u-phase secondary winding, the second v-phase secondary winding, and the second w-phase secondary winding has a first end connected to an AC side of the first rectifier element or the second rectifier element of a corresponding phase, and a second end connected to the secondary side neutral point; 5. The DC power supply device according to claim 4, wherein each of the first x-phase secondary winding, the first y-phase secondary winding, the first z-phase secondary winding, the second x-phase secondary winding, the second y-phase secondary winding, and the second z-phase secondary winding has a first end connected to the secondary side neutral point, and a second end connected to the AC side of the first rectifier element or the second rectifier element of a corresponding phase.

6. 3. The DC power supply device according to claim 1, wherein each of the first rectifying element and the second rectifying element is formed of a thyristor controlled to have a conduction angle of 150 degrees.

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