JPH0332366A - Rectifier circuit device - Google Patents

Abstract

PURPOSE:To reduce size and cost of a rectifier circuit device by connecting a reactor between negative output lines of first and second bridge rectifiers. CONSTITUTION:In a thyristor rectifier circuit device, a noninsulating transformer 20 of side-extension delta-connected type is connected between AC power source terminals 1-3 and first, second 3-phase bridge rectifiers 5-6. Positive output lines 5a, 6a of the rectifiers 5-6 are respectively connected to positive and negative output terminals 8-9 through an interphase reactor 7, negative output lines 5b, 6b are respectively connected thereto through an interphase reactor 24, and further connected to a load 10. The bridge rectifiers 5-6 are controlled by a controller 27.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Utilization] The fourth aspect relates to the construction of a rectifier circuit in which a plurality of bridge rectifier circuits are connected in parallel.

[Conventional technology]

A conventional 12-phase thyristor rectifier circuit is constructed as shown in FIG. In this rectifier circuit, a first insulating transformer 4 is connected to the three-phase AC power supply terminal A1,2,3 at t6.
These three-phase fringe rectifier circuits 5.6 are connected via an interphase reactor 7, and one output terminal 8 is connected to the midpoint of the interphase reactor 7. is connected, and the other output terminal 9 is connected to the negative side line of each rectifier circuit 5.6.

Therefore, power is supplied to the load 10 from both the first and second thyristor three-phase Brisoji rectifier circuit 11'1♀5.6. ,
It consists of a first secondary winding 12 with a star-shaped connection and an i2 secondary winding 13 with a triangular connection. The output voltage of the first secondary winding 12 and the output 'E pressure of the second secondary winding 13 are mutually π/6
It has a phase difference of Therefore, a 12-phase rectified output of 4 dTi can be obtained from the 2.1 ift three-phase bridge rectifier circuit 5.6, and harmonic components of the input current can be reduced. A current detector is connected to the positive output line of the first thyristor filter phase bridge rectifier circuit 5.6 and the second thyristor filter phase bridge rectifier circuit 5.6. These lJj forces are applied to a control circuit (not shown) which forms control pulses for the thyristors 7iJJ and the second thyristor filter bridge 'J jAi circuit 5.6.

In addition, in this conventional circuit, the insulating transformer 4 is used, and no direct circulating current flows therethrough. Therefore, the control by the current reduction lJj (d, circulating current 1s) is not stopped, but in order to prevent the current from flowing unevenly in the first and second thyristor filter bridge rectification path 5.6, be done.

[Problem where the output power is guaranteed to be 7 ri] In the circuit shown in Fig. 8, two sets of rectifier circuits 5.6 are connected to a pair of mutually insulated secondary windings 12.13, so that the circulating current lAt It has the characteristic that it flows easily and is difficult to use.

However, an isolation transformer has lower efficiency than a non-isolated transformer, is larger, weighs more, and is more expensive.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a rectifier circuit device that can be made smaller and lower in cost.

Step 1 for solving the problem] J.: The invention according to claim 1 for achieving the above object is:
a non-isolated transformer connected to an AC power supply, at least first and second bridge rectifier circuits connected to the non-isolated transformer, a positive output line of the first bridge rectifier circuit and the second bridge rectifier; a first reactor connected between the negative output line of the first bridge rectifier circuit and the negative output line of the second bridge rectifier (b) path of the circuit; the second connected between
reactor, a positive output terminal connected to the midpoint of the first reactor, and a positive output terminal connected to the midpoint of the first reactor, and a
and a negative output terminal connected to 11 points7.
．． ＜ As a percentage! This relates to an f-flow circuit device.

In the present invention, the non-insulated transformer is, for example, a transformer with side-extended triangular connection, or a double-circuit connection. The circuit is a bridge rectifier circuit or a diode bridge rectifier circuit.-Also, the first and second reactors may each be a center tap type reactor, or may be independent reactors connected in series to each line. (・.

In the invention according to claim 2, the bridge rectifier circuit path is constituted by a thyristor, and current detectors are provided for detecting the currents of the 0 and 0 output lines, respectively, and the first and second In order to control independently the positive side thyristor and the negative side thyristor of at least one of the thyristor bridge rectifier circuits, the positive side control circuit and the negative side 1rlJ are used.
The control circuit plays a role.

The positive side control circuit 'f#1 includes, for example, the positive side current balance detection circuit 28, the addition circuit 34, and the phase control circuit 32 of the embodiment.
The negative side control circuit F6 is a circuit portion consisting of, for example, the negative side current balance detection circuit 22, the addition circuit 35, and the phase control circuit 33.

In the invention set forth in claim B, the currents on the input sides of the first and second thyristor bridge rectifier circuits are detected, and the current components of the positive side and negative side output lines are determined by calculation based on the detected currents. Similarly to the invention, the currents of the positive side thyristor and the negative side thyristor are controlled.

[For production]

Since the present invention uses a non-isolated transformer, size reduction and cost reduction can be achieved. Note that there is a risk that freewheeling current may flow due to the use of a non-isolated transformer; Since the reactors were also connected and the output terminal was connected between each reactor, the circulating current was suppressed.

In the invention of Claim 2 and B, the positive 1rtu and negative side currents of the first and second thyristor bridge rectifier circuits are respectively detected or detected, and the first and second thyristor bridge rectifier circuits are adjusted so as to balance each other. Since at least one positive side thyristor and one negative side thyristor are controlled respectively, it is possible to maintain a good current balance.
, freewheeling current is prevented and the alternating current input current becomes a near-sine wave.

〔Example〕

Next, with reference to FIGS. 1 to 5, the thyristor rectifier circuit device according to the embodiment of "Non-explosion" will be explained.

However, in FIG. 1, parts that are substantially the same as those in FIG. 8 are designated by the same reference numerals, and their description will be omitted.

In this embodiment, the AC power supply terminal 1.2, the first and second filter phase bridge rectifier circuits (hereinafter referred to as first and second bridge circuits) 5.6 and fbfJ. One non-insulated transformer 20 of triangular connection with extended sides is connected.

This non-insulated transformer 20 is a single-turn transformer, and the first
, in addition to the main windings 21.22.23 of the second and third phases, extension windings 2ia, 21b, 22a, 22b, 23a, 2
It has 3by. In addition, the windings 21.21 a, 21bU in phase 1 winding 22.22 a, 221] are in phase, the winding 23.2
3a, 231) are in phase. 3-phase power terminal 1.2.3
is connected to the connection point of the triangular connection of six main windings 21, 22, 23 having the same number of windings, and the first and second bridge circuits 5.6 are connected to the connection points of the triangular connections of the six main windings 21, 22, 23 having the same number of turns, and the first and second bridge circuits 5.6 are connected to the respective extension windings 21a, 21b, 22a, 22b
, 23a, 23b's peak terminals U1, U2, vl, v2,
W, , W2. j・Lance output terminal [J
,,vl,WJ voltage phase is input power supply terminal 1.2,
The voltage phase of transformer power terminals U2, V2, W2 has a difference of 1π/12 with respect to the phase of input power supply terminal 1.2.5. .

Positive side Nyristors S1, s2 of the first bridge circuit #S5,
The connection midpoint between S3 and the negative thyristors S4, S5, and s6 is connected to the output terminals Ul, V, and W of the transformer 20, respectively, and the positive thyristors s7 and S of the second bridge circuit 6 are connected to the output terminals Ul, V, and W of the transformer 20.
The two points connected to the negative side Zyristors S+o, S+1, and S12, such as 8 and S9, are the output terminals Ul, v2, and W of the transformer 20.
, J sole are connected respectively. The positive 1fj lines 5a, 6a of the first and second bridge circuits 5.6 are connected to the positive 1 output terminal 8 via the interphase reactor 7, respectively,
The negative output lines 51] and 6b are also connected to the negative output terminal 9 via the mutual reactor 24. Na'! 6. The positive and negative edge terminals 8.9 are connected to the center tap of the interphase reactor (-roof, 24. Note that the reactor I. It is also possible to divide it into two reactors on the second bridge circuit 6 side.

In this case, 1'lj: Output terminal 8, ? at the connection midpoint of the two reactors. Connect. First and second bridge circuits 5
．． Each mountain of 6 Kaline 5a, 5b, 6a, 61) K
are connected to current detectors 14, 15, 25, and 26, respectively.

Is the detection line of each current detector 14, 15, 25, 26 on the positive side for current balance compensation of the control circuit 27? Ii style uneven balance detection circuit 28 side power 1#;/clamp detection circuit 29
Toni] Became a concubine.

The control circuit 27 includes a positive and negative side current balance detection circuit 28
．． In addition to 29, it has an output voltage command value input terminal 30, first, second, and third phase control circuits 31, 32, 33, addition circuits 34, 35, and a reference clock circuit '#536. Output voltage command value input terminal OE1 and reference clock circuit 36
is connected to the first phase control circuit 3, and when the output voltage command is constant, the positive side and negative side thyristors 81 to S6 of the first bridge circuit 5 are driven with a fixed phase.

The first calo calculation circuit 34 is the positive side current balance detection circuit 28
and the output voltage command value input terminal 30, and the added value of the signals obtained from these is sent to the second phase control circuit 32.
i'i knee/-j eru. Second addition circuit 55 negative side current balance Yokota circuit 29 and L13 voltage command value input terminal 3
D, and the sum of the signals given from these is given to the third phase control circuit 33.

The second phase control circuit 32 generates a signal to control the positive side thyristors S7, S8, and S9 of the second bridge circuit 6, and the fifth phase control circuit 53 generates a signal that controls the negative side thyristors S7, S8, and S9 of the second bridge circuit 6. Sho, S1□, SI2 'tK Generates control signals. The second phase control circuit 32 controls the first and second positive side mountain lines 5a and 6a. The positive-side Zyristers S7, S8, and S9 are controlled so that the currents are balanced, and the third phase control circuit 33 is controlled so that the currents in the first and second negative-side output lines 5b and 6b are balanced. Negative side thyristor SI Os SI I, SI2 is controlled by 1liU.

The reference tarlock circuit 36 provides reference timing for the first, second and second phase control circuits 31, 32, 33.

FIG. 2 shows in detail the positive side current leak detection circuit 28 and adder circuit 34 of FIG. The first input terminal 41 is the first
The second input terminal 42 is connected to the positive current detector 14 of
is connected to the second positive current detector 15. - Resistors 43, 44 are connected between the power input terminals 41, 42, and during these connections A is connected to an operational amplifier 46 via a resistor 45.
is connected to one input terminal of the An integrating capacitor 4 and a resistor 48 are connected between the negative input terminal and the output terminal of the operational amplifier 46, and the other input terminal is grounded. Note that first and second positive current detectors 14.15 are connected to the first and second input terminals 41.42 with opposite polarities.

Therefore, when the peak values of the first and second positive current detectors 14.15 are equal, the connecting midpoint 49 of the deferred payment 43.44
When the electric potential becomes zero and the current becomes unbalanced, the electric potential becomes positive or negative.

The addition circuit 34 consists of resistors 50, 51, 52, 53, arithmetic increaser 11, etc. 9, and an output voltage command value input terminal 60.
1 upper blade voltage of the balance detection circuit 28 is added to the voltage given from the balance detection circuit 28, and the result is output.

The negative side current balance detection circuit 29 and the addition circuit 35 are not shown in FIG. 2 and have the same configuration as the positive side current balance detection circuit 28 and the addition circuit 34.

FIG. 3 shows the first phase control circuit 31 of FIG. 1 in detail. The first phase control circuit 31 includes sawtooth wave generation circuits 61, 62, 6, and 6 for generating six sawtooth waves corresponding to the thyristors 81 to S6 of the first bridge circuit 5.
It has 4.65.664.

The six sawtooth wave generating circuits 61 to 66 generate six sawtooth waves 2 as shown in FIG. 5
The sawtooth waves in Figures (4) to (G) are generated by the first bridge circuit 5.
As shown in the drawing, there is a mutual phase difference of 2π/3. Note that the positive side thyristors s1, s2, and s3 and the negative side thyristors S4, S5, and S6 have an inverse phase relationship, and have a phase difference of π.

1st to 6th comparators 67.68.69.70.7
One input terminal of 1.72 is the output voltage command value input terminal:
60 respectively, and the other input terminal is connected to the first to sixth input terminals.
Therefore, the comparators 67 to 72 generate control pulses corresponding to the period in which the sawtooth wave crosses the output voltage command value, respectively. The control pulse of drive circuit 73.
Thyristor 81 via 74.75.76.77.78
What about the thyristors S1-s6 given to the gate of ~S6? f
Conduction starts in synchronization with the rising edge of the ilJ al pulse.

Figure 4 shows the second and third phase 1fiU control circuits 32 and 33.
shows. The first phase control circuit 32 includes five sawtooth wave generating circuits 81, 82, 8, and three comparators 84, 8.
5.86, and three drive circuits 87, 88, and 89. The Zyristors S7 and S shown in FIG.
8. The sawtooth wave for S9 is a comparator 84.85.8
6 and the first adder circuit 34 provides the first
A control pulse is generated corresponding to the period in which the sawtooth wave crosses the first control signal, and is applied to the holomorphic Zyristers S7, S8, S of the second bridge circuit 6. It will be done.

The third phase control circuit 33 includes thyristors Soo and So
, 812 three sawtooth wave generation circuits 90.91
．． 92, three comparators 93, 94, 95, 6
It consists of three drive circuits 96, 97, and 98. FIG. 5f,]'l generated from sawtooth wave generating circuits 9D, 91.92
(Ill [T, The sawtooth wave shown in l is the comparator 9
3.94.95 is compared with the second control signal provided from the second summing circuit 35, and a control pulse is emitted corresponding to the period in which the sawtooth wave crosses the second control signal. LL
, negative side thyristor Sho, S of the second bridge circuit 6
11, is given to the gate of S12.

5 (G) corresponding to the thyristors S7 to SI2 of the second bridge circuit 6 - [The sawtooth wave of Ll is shown in FIG.
4) Each of the waveforms is ahead of the sawtooth waves of (g) by π/6. The first and second side extension triangular connection transformer 20
Bridge circuit 5.6 of 12 thyristors So”
Do the voltages applied to SI2 each have a phase difference of π/6? The 12 sawtooth waves shown in FIG. 5 (4) to crests correspond to the phase difference between the voltages of the thyristors 81 to SI2.

Assuming that the voltage value of the output voltage command 1IIT input terminal 3D is fixed, the thyristors 81 to S6 of the first bridge circuit 5 conduct with a fixed phase, but the thyristors 81 to S6 of the second bridge circuit B ~S, does not conduct at a fixed phase, but conducts at a phase that corresponds to the change in the level of the control signal given from the adder circuit 34.35 in Fig. 4 1'7m. If there is an imbalance between the current in the output line 5.] and the current in the second positive output line 6a, this is compensated for.
The conduction phase of 7, S8, and S9 changes, and the first (1)
The current in the output line 5b of fl and the second negative output line 6
If there is an unbalance between the current of b and the current of U, the thyristor 5i (1, sll, SI
The conduction phase of 2 changes. Therefore, the first bridge circuit (5 vertically 1 thyristors S, , S2, S3 and a load 10
and the negative one iris S+o of the second bridge circuit 6,
811. Circulating current χ in the closed circuit consisting of Sl2 and lance 20 can be prevented. If the transformer 20 is not insulated and the current is unbalanced, a circulating current will flow in the closed circuit, and the input power terminal 1
．． 2.5, the harmonic components of the current waveform increase.

Note that if the output voltage command direct input terminal 30 (7) voltage changes, the phases of the 12 thyristors S+-SI2 change simultaneously, achieving stabilization control or adjustment of the output voltage.

[Modified example]

The present invention is limited to one embodiment, and there are four, for example, the following variations are possible.

+1. l As shown in FIG. 6, the positive and negative output lines 5a, 51 of the first and second bridge circuits 5.6;
6a and 6b are current detectors 14. a, 15a, 25a
, 26a, respectively, to form the current balance detection circuit 10.
Also added 0.101, current balance detection circuit 100.1
01 (Even if Ci-3, current balance detection circuit 28.
Similarly to 29, the 7h flow balance is detected and added to the 17h voltage command value in addition circuits 102 and 103 to obtain the phase i.
1j control time control 1a, 31bK may be input. The phase a51J control circuits 3ia, 31b control the phase control circuit 31 of FIG.
It is divided into 6 groups, and is formed in a +'c configuration similar to the phase control circuits 32 and 33 in FIG. Note that in FIG. 6 and FIGS. 9 to 11, which will be explained below, sounds 1j that are substantially the same as those in FIG. 1 are designated by the same symbols.

As shown in Figure 6'17: First and second bridge circuit 5
．． Even if both circuits 6 are controlled to balance the current, the same effect as the circuit shown in FIG. 1 can be obtained.

k, current detection k 14 a, 15a, 25a, 26a
Current detector 14.15.25.26
You can also use it for both l and n.

+21 Instead of the side extension triangular connection transformer 20 shown in FIG. 1, a fork connection non-insulated transformer 20a shown in FIG.
'x can be used. In addition, in FIG. 7, the electric currents F:f, rJ of the windings a2, bl, and c2 have a phase difference of 120 degrees, the windings al, a2, a3, and a4 are in phase, and the windings bl, bl, b3 and b4 are in phase, winding C], C2s
c3 and c4 are in phase. Further, in FIG. 7, illustration of the t/'i current detection path 171J and the control circuit is omitted.

(3) Instead of detecting the currents in the output lines 5a, 5b, 6a, 6b of the first and second bridge circuits 1135.6, the currents Mt on the input sides of the first and second bridge circuits 5.6 are detected. A current detector for detection is also provided on the input line, and based on the output of these current detectors are connected to the peak line b of the bridge circuit 5.6.
A circuit for calculating the currents of a, 5b, 6a, and 6b may be provided.

(4) A fixed voltage can be applied to the input terminal 3DK.

(51 reference clock to each sawtooth wave generating circuit 61 to 66.
Instead of supplying 81-83.90-921/i1m, the serrations of thyristor S1'? The sawtooth waves of the remaining Nyristors 82 to S12 may be created based on the &, etc. standard.

+61 As shown in FIG. 9, the first and second bridge circuits 55.6 are connected to diodes D1-D6 and D7-. 1
) 12 diode bridge rectifier circuit. In the case of a diode bridge circuit, no control circuit is provided since the control of the current balance (I"i and "C") is not provided. However, the positive and negative output lines 5
interphase reactor 7 in any of a, 51), 6a, and 6b.
．． 24 is connected, the circulating current is suppressed.

(7) The Xyristor bridge circuit 5.6 in Fig. 7 is
It can be replaced with a diode bridge circuit 5.6 consisting of diodes D1 to D12 as shown in FIG. Note that in the case of a diode, the heavy Mf, Yokoyama circuit, and control circuit become unnecessary.

(8) As shown in Figure 11, 12 output terminals U
,,IJ2,U,3,U4,Vl,V2,■3,v4,
A fork-connected non-insulated transformer 2DI having Wl, W2, W3, and W4 is used, and the first, second, third, and fourth bridge circuits 5.6.110.111 are connected to this, and a 24-phase A rectifying path may also be provided. Bridge circuit 5.6, 110 in Fig. 11, I'1lid diode D1~
D24 constitutes a three-phase bridge circuit. The positive outputs 5a, 6a, 110a, 111a of each syringe 1 channel 5.6, 110.111 are reactor 7a,
After being paralleled via 7b, 7c, and 7d, it is set to H. It's 1.
Negative output line 5b, 61v, 110b, Il'll]
! d Reactor l-24 a, 241], 24c, 24d
are sucked in parallel via the reactor 7a.
, 71), 7c, and 7d are constructed by installing the sensing core 112 I/C winding as shown in the 131st flash ((as shown).Reactors 24a, 24b, 24c, 24
d is also constructed in the same manner as in FIG.

The non-insulated transformer 20b of the 11th mountain has the first phase tube, line al, a21, 13.2 as shown in 121E71.
'4, a5, a6 and the second O]] Volume 11Jb+, b
2, b3, b4.1)5.1]6 and third phase winding c
1, C2, C3, C4, C5, and C6. First,
A phase difference of 120 degrees is applied to the second and second filter phases (iJ: Fj, s). has been done.

(9112 phases, 24 phases ((without limitation, 18 phases, 36 phases)
The present invention can also be applied to a circuit with a polyphase rectifier M' having equal phases.

〔Effect of the invention〕

As is clear from the above, according to the inventions of claims 1.2 and 2, it is possible to reduce the size and sales cost of the rectifier, and also to reduce the circulating current generated by providing a non-insulated transformer. building can be prevented.

4. Figure ``Simple explanation of Fl'' Figure 1 is a circuit diagram of a thyristor rectifier circuit according to an embodiment of the present invention; Figure 3 is a block diagram showing the first phase control "1 path" in Figure 1. Figure 4 is a block diagram showing the second and third digits and 1 in Figure 1. Figure 5 is a block diagram showing the control circuit I; Figure 5 is a waveform diagram showing the output of the mine-shaped wave generating circuit shown in Figure 3; Figure 6 is a modified example of Zyristor rectification [IIJ Fig. 7 is a circuit diagram showing a thyristor rectifier circuit device 2 of another modification; Fig. 8 is a circuit diagram showing a conventional thyristor rectifier circuit device; Figs. 9, 10, and 11 12 is a circuit diagram showing a rectifier circuit device according to another modified example of the present invention, and FIG.
FIG. 13 is a circuit diagram showing the J-lance shown in the figure, and FIG. 1 is a front view showing the reactor shown in FIG. 12.

1.2, Lo...power supply terminal, 5. 1st thyristor 5-phase bridge rectifier circuit, 6.E2 Zyristor filter phase bridge rectifier circuit 1, 7..interphase reactor 15.current detector, 20 Non-isolated transformer, 24 phase reactor, 25,
26. Current detector, 28. Positive side current balance detection circuit, 29. Negative side current balance Yokota circuit, 30 Output voltage command 1 direct input terminal, 31.. 1st phase ffiIJ Gokakuji, 32. 2nd phase Phase control circuit, 33, fifth phase control circuit, 110...-third thyristor three-phase bridge rectifier circuit, 111 fourth thyristor three-phase bridge rectifier circuit,
, Agent Noriyuki Takano (LIL)

Claims (1)

[Scope of Claims] [1] A non-isolated transformer connected to an AC power supply, at least first and second bridge rectifier circuits connected to the non-isolated transformer, and a positive terminal of the first bridge rectifier circuit. a first reactor connected between an output line and a positive output line of the second bridge rectifier; a negative output line of the first bridge rectifier and a negative output line of the second bridge rectifier; a second reactor connected between the output line of the first reactor, a positive output terminal connected to the midpoint of the first reactor, and a negative output terminal connected to the midpoint of the second reactor. A rectifier circuit device comprising: [2] A non-isolated transformer connected to an AC power source, at least first and second thyristor bridge rectifier circuits connected to the non-isolated transformer, a positive output line of the first thyristor bridge rectifier circuit, and the a first reactor connected between the positive output line of the second thyristor bridge rectifier circuit; and the negative output line of the first thyristor bridge rectifier circuit and the negative output line of the second thyristor bridge rectifier circuit; a second reactor connected between the output line; a positive output terminal connected to the midpoint of the first reactor; and a negative output terminal connected to the midpoint of the second reactor. , first and second positive side current detectors for detecting the currents of the positive output lines of the first and second thyristor bridge rectifier circuits, respectively; first and second negative side current detectors for respectively detecting currents in negative output lines; 1st
and a positive side control circuit that controls at least one positive side thyristor of the first and second thyristor bridge rectifier circuits in response to the output of the second positive side current detector; Said first thyristor bridge rectifier circuit so that the currents of the negative output lines of the
and a negative-side control circuit that controls at least one negative-side thyristor of the first and second thyristor bridge rectifier circuits in response to the output of the second negative-side current detector. [3] A non-isolated transformer connected to an AC power supply, at least first and second thyristor bridge rectifier circuits connected to the non-isolated transformer, a positive output line of the first thyristor bridge rectifier circuit, and the a first reactor connected between the positive output line of the second thyristor bridge rectifier circuit; and the negative output line of the first thyristor bridge rectifier circuit and the negative output line of the second thyristor bridge rectifier circuit; a second reactor connected between the output line; a positive output terminal connected to the midpoint of the first reactor; and a negative output terminal connected to the midpoint of the second reactor. , current detection means for detecting the input currents of the first and second thyristor bridge rectifier circuits, respectively; and positive and negative outputs of the first and second thyristor bridge rectifier circuits based on the outputs of the current detection means. current calculation means for calculating the currents of the lines, respectively; and a current calculation means for calculating the currents of the positive output lines of the first and second thyristor bridge rectifier circuits based on the positive side currents obtained by the current calculation means. a positive-side control circuit that controls at least one positive-side thyristor of the first and second thyristor bridge rectifier circuits; and a positive-side control circuit that controls at least one positive-side thyristor of the first and second thyristor bridge rectifier circuits; and a negative side control circuit that controls at least one negative side thyristor of the first and second thyristor bridge rectifier circuits so that currents in negative output lines of the rectifier circuit are balanced with each other.