JPH01264569A - Power converter - Google Patents

Abstract

PURPOSE:To reduce pulsations by newly installing a changeover circuit and an auxiliary circuit composed of auxiliary windings for two pairs of interphase reactors equipped with a plurality of taps. CONSTITUTION:The AC side input terminals U1-W1, U2-W2 of one three-phase bridge rectifier circuit 1 using thyristors T1-T6 as rectifying devices, the other three-phase bridge rectifier circuit 2 employing thyristors T7-T12 as rectifying devices, and a three-phase AC power supply 3 are connected in series at nodes U-W. The positive pole terminal P and negative pole terminal N of the DC side outputs of the three-phase bridge rectifier circuits 1-2 are connected respectively through main windings 4a, 4a' for interphase reactors 4, 4', and an auxiliary circuit 7 and a series circuit 5 are connected in series between the midpoints Oa, O'a of the interphase reactors. The auxiliary circuit 7 is composed of auxiliary windings 4b, 4b' and a changeover circuit 6 using auxiliary thyristors TO, TP1, TQ1, and the midpoints Oa, Ob of the main winding 4a and the auxiliary winding 4b are connected directly. Accordingly, the AC side current waveforms of both circuits 1-2 take a stepped waveform, and the waveforms are synthesized and the AC current waveform of the AC circuit 3 is acquired.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a power conversion device, and more specifically, to reduction of harmonics of AC side current and pulsation of DC side voltage of a power conversion device. be.

"Prior Art" Conventionally, in power conversion devices such as rectifiers, the AC side current of the power exchange device includes harmonic components, while the DC side voltage includes pulsating components. If the harmonic components contained in this AC side current (hereinafter referred to as harmonic current) do not flow to the AC power supply side, especially to the power grid, the AC power source may cause burnout, heating, etc. to various devices connected to the power grid. This has caused widespread problems such as malfunctions. On the other hand, the pulsating component included in the DC side voltage can also cause trouble in the DC power supply or various equipment connected to the DC side of the power converter, so it is essential to install a DC filter using a reactor or capacitor. Met. However, the size and weight of the DC filter are large, contributing to the increase in size and cost of the power converter. For this reason, in the past, efforts have been made to reduce harmonic currents and pulsations in the DC side voltage by multiplexing power conversion devices, increasing the number of pulses, and the like.

In Fig. 9, as an example of conventional multi-type multi-phase conversion,
The circuit of the phase silis bridge 12 pulse rectifier will be shown and explained. The dual three-phase Xyristor bridge 12-pulse rectifier shown in Fig. 9 is a known one, and is a dual three-phase Xyristor bridge 12-pulse rectifier circuit with interphase reactors consisting of a combination of star-shaped and triangular connections. have.

In FIG. 9, a three-phase bridge rectifier circuit 1 having thyristors 1 to 6 as rectifying elements is connected to one secondary winding 8b of a star-connected transformer 8, and the thyristor 1 1~. A three-phase bridge rectifier circuit 2 with 'U1□ as a rectifier is connected to the other secondary winding 8 of a triangularly connected transformer 8.
C, and the primary winding 8a of the transformer 8 is connected to the three-phase AC power supply 3. , and both three-phase bridge rectifier circuits 1 and 2 are connected on the positive pole side of the DC part through Pa and Qa, which are the ends of the winding 4a of the interphase reactor, and on the positive pole side of the DC part at point O'a, V[ A DC voltage is applied to a load 6 which is connected afterwards and is connected between the midpoint Oa of the winding 4a of the interphase reactor and the connection point 0'a via a DC fill reactor 1-5 for pulsation reduction. It is designed to supply

During normal operation of this two-type three-phase thyristor bridge 12-pulse rectifier, the DC output voltages etx and ea- of both three-phase bridge rectifier circuits 1 and 2 are determined by the magnitude of the control angle α of the thyristors 1゛1 to 1゛1□. The waveform changes depending on the control angle α, but if the control angle α is about 60 [dO(I)], if the overlap is ignored, the waveform will be 30 [dO
It becomes a sawtooth wave including a pulsating component with a phase difference of 6, f<f is the power supply frequency), and the voltage e di! between terminals Oa and O'a is generated. Ce dt! = (e d+je d2)
/2] is a sawtooth wave including a pulsating component of 12f, and the voltage V applied across the winding 4a of the phase reactor, (V-edl
ed□) becomes a substantially square wave of 6f as shown in FIG. 10(b). On the other hand, each AC input current js+, is□ of both three-phase bridge rectifier circuits 1 and 2 becomes a 120-degree reversible square wave AC waveform as shown in FIG. The combined current im of the three-phase AC source 3 is the first
This results in a 12-pulse staircase waveform as shown in Figure 0 (C).

In order to further increase the number of pulses, it is necessary to use a staggered winding, etc.
A triple three-phase bridge 18-pulse system that combines a transformer with two sets of windings, three three-phase bridge rectifier circuits (consisting of 18 rectifying elements), and three interphase reactors to create 18 pulses. A rectifier circuit is used.

``Problems to be Solved by the Invention'' In this way, in order to implement the multi-pulse design of the prior art, it is necessary to use a transformer with multiple windings and a large number of conversion circuits (the same number of rectifiers as the number of pulses). ), and the control becomes complicated, resulting in a significant increase in the size and cost of the power converter as a whole.

In view of the above prior art, the present invention eliminates the need for a large and expensive transformer, further reduces the number of rectifying elements, and economically eliminates harmonics of the AC side current and DC ff! The present invention aims to provide a conversion device that reduces pulsations in I voltage.

"Means for Solving the Problems" FIG. 1 shows the configuration of a power conversion device according to the present invention for achieving the above object. The power conversion device according to the present invention has two
#AC terminal tJ+ of JI three-phase bridge conversion circuit 1, 2
, V+ , W+ and U 2 +' V 2 , W2
．． are directly connected to U, V, and W of the 3-phase AC concave U'63, respectively, and the DC side positive ends P++ and Pd□ of both the 3-phase bridge conversion circuits 1 and 2 are connected to the main winding 4a of the interphase reactor 4.
, and the DC side negative terminals N d+ and Nd□ are connected to each other via the main winding 4'a of the new interphase reactor 4'. In the two sets of interphase reactors 4, 4', each main winding 4a.

The two sets of auxiliary windings 4b, 4'b are provided with a plurality of taps.
Each tap of 4'b corresponds to a respective winding 4b.

Each winding 4b is symmetrical about the midpoint of 4'b.

4'b, each tap of one auxiliary winding 4b is connected to an auxiliary switching element (S P+).

5p2---andS. and S or , S Q
2----) The switching circuit Ii! 86 to each tap of the other auxiliary winding 4'b.

Auxiliary port 1i1 consisting of the two sets of auxiliary windings and switching circuit 6
At one end of the 87, the main winding m4a of the positive interphase reactor 4 and the midpoints Oa and O'a of the auxiliary winding 4b are directly connected, and at the other end of the auxiliary winding 4'b of the negative interphase reactor 4'. The midpoint 0'b is connected to -@P of the DC circuit 5. Alternatively, the auxiliary circuit 7 can be connected to each midpoint 0'a of the main winding 4'a and the auxiliary winding 4'b of the negative phase reactor 4'.
and O'b are directly connected, and the other positive electrode side phase reactor 4
A power converter is constructed by connecting the midpoint Ob of the auxiliary winding 4b to one end P of the DC circuit 5.

1 action'' In this way, the switching circuit 6 and the auxiliary winding 4b of the two navy blue interphase reactors 4, 4' having a plurality of tags.

By newly installing the auxiliary circuit 7 consisting of 4'b,
The voltage e4 of the DC circuit 5 is changed by a portion of the auxiliary windings 4b, 4b of the two pairs of interphase reactors 4, 4' selected by the switching recess 1i46 to the voltage e4 of the two three-phase bridge conversion circuits 1.
．． 2 DC side voltage eat, e (point O which is the average value of 12
Voltage e da between a and O'a (point Oa where e da is applied,
-P voltage edβ sum (ed = e da-1-
edβ). Here, the voltage edβ obtained by the auxiliary circuit 7 differs depending on the number of taps provided in the auxiliary circuit 7, but it becomes a stepped AC waveform and the main winding 4a of the two sets of interphase reactors 4, 4'.

It acts on the voltage V□ induced in 4a, and the voltage ■.

The waveform changes stepwise. As a result, the pulsation of the edα is offset by the edβ, and the pulsation of the voltage ed of the DC circuit is reduced.

On the other hand, since the current Id of the DC circuit 5 is divided into ampere turns by the two sets of interphase reactors 4 and 4', or the current Id passes through the auxiliary circuit 7, the current Id is passed through the auxiliary circuit 7 between the two sets of interphase reactors 4 and 4'. Auxiliary winding 4b of reactor 4, 4',
It will pass through 4b.

The ampere turns generated in the auxiliary windings 4b, 4b are caused by the operation of each switching element constituting the switching circuit 6 (S P+
, S p7−−−−5o−−−−8Q2+ S or
,), but the number of Sode Suke volume #! 4b, 4b and the main windings 4a, 4a of the phase reactors 4, 4' are magnetically coupled, so that the auxiliary windings 4b, 4. The ampere turn generated in the main windings 4a, 4a is induced in the main windings 4a, 4a. This causes the phase reactor 4. /1°7.2 idl, id2 and idl, 1d2 are distributed by ! The currents generated by the ampere turns of the auxiliary windings 4b and 4b are superimposed, resulting in an uneven current waveform. Therefore, the AC side current waveform of the two-string three-phase bridge conversion circuit 1.2 becomes a stepped waveform, and the AC current waveform in the three-phase AC circuit 3 is the AC current of the two sets of three-phase bridge conversion circuits 1.2. Either a waveform or a synthesized waveform. Since this synthesized waveform becomes a multi-pulse waveform, it becomes a waveform with reduced harmonic components.

"Example" Embodiments according to the present invention are shown in FIGS. 2 to 8.

FIG. 2 shows an embodiment in which the present invention is applied to a separately excited rectifier, FIGS. 3, 4, and 5 are diagrams explaining the operation of each part in FIG. 2, and FIG. FIG. 7 shows an embodiment in which the present invention is applied to an excited rectifier, FIG. 7 shows an embodiment in which the present invention is applied to a reactive power supply device, and FIG. 8 shows an embodiment in which the present invention is applied to a separately excited inverter device. The present invention will be explained in detail in the embodiment shown in FIG. In Fig. 2, the AC side of one three-phase bridge rectifier circuit 1 with thyristors '■゛1 to '■゛6 as rectifying elements and the other three-phase bridge rectifier circuit 2 with thyristors 'F7 to T1□ as rectifying elements. Input terminals U+, V+, W+ and U2. V2. W2 and 3-phase AC power supply 3 connection point LJ,
They are directly connected by V and W. The F terminal P dl + Pd□ and the negative terminal N dl + N d2 of the DC side outputs of the three-phase bridge rectifier circuits 1 and 2 are connected via main windings 4a and 4a with phase-to-phase reactances 4 and 4', respectively. , the main winding 4. a,, midpoint Oa of 4a.

0'a, the auxiliary circuit 7 and the DC circuit 5 are connected in series. The auxiliary port 1187 is connected to the auxiliary winding 4 having intermediate taps provided at the two sets of interphase reactors 4, 4°.
b, 4b and auxiliary thyristor 'ro.

It is constituted by a switching circuit 6 using Tp + and T o +, and both ends P of the auxiliary windings 4b, 4b facing each other
I.

P'l and Ql, Q'l and midpoints Ub and Ob, respectively, are connected to the auxiliary thyristor T Pl+ rp Ql+ T
It is connected via o. Also, the midpoints Oa and Ob of the main winding 4a and the auxiliary winding 4b of the phase reactor 4 are directly connected, and the midpoint O'b of the auxiliary winding 4b of the phase reactor 4' is connected directly.
is directly connected to one end P of the DC circuit 5.

The DC circuit 5 has a DC filter reactor 5a and a DC load 5b connected in series.

The operation of FIG. 2 of this embodiment will be explained using the operation explanatory diagrams shown in FIG. I will explain. In the description, each thyristor 'I' + ~T'
+2. To, 'I'p+, and To+ are ideal switches, the three-phase AC power supply 3 is a three-phase symmetrical sine wave, and the excitation current, winding resistance, and leakage reactance of each phase reactor 4, 4' are ignored. Further, the interface of the DC filter reactor 5a is sufficiently large and the DC output voltage Id is kept constant and smooth. Also, the phase reactor 4 of #2 above
．． The number of turns of each winding 4' Pa Qa, P'aQ'a, Plo, and P + O'- is Na, N'a, Nb, respectively.
, N'b, and further Nb/Na = N'b/N'
Let a=Am -----(1).

If the operating period of each thyristor '[1-'12 of the two sets of three-phase bridge rectifier circuits 1 and 2 is controlled as shown in FIG. 3(b), the three-phase bridge rectifier circuit 1 of the 2 2
DC output voltage edl+e! +12 is the pulse 12 of 3C (f is the frequency of the three-phase AC power supply 3) as shown in Fig. 3(a).
- It becomes a sawtooth waveform including a single motion, and the midpoints Oa, O' of the main windings 4a, 4a of the two sets of interphase reactors 4,4'
The voltage eda between a is the average value e of the voltage eat and Qa2.
da-(e at + e a2) /2, and the voltage eda has a sawtooth waveform including a 6f pulsation component, not shown in FIG. 3(a). On the other hand, if the voltages applied to the main windings 4a, 4'a of the mutually facing axles 4, 4° are respectively Vma and V'ma as shown in FIG. 2, then the sum is Vm (Vm = Vma) - V'ma) is the difference between the voltage e+++ and Qa2 (Vm = e dl e d
l), and the voltage Vm is 6 as shown in FIG. 3(d).
It becomes a substantially square wave of f. Moreover, a voltage expressed by the following equation is always induced between each terminal of the two sets of auxiliary windings 4b, 4b, and if the commutation type turning angle is ignored, the auxiliary thyristors T − and T p+.

It is possible for two or more of 'F91 to be conductive at the same time; a reverse voltage is applied to one of them. Therefore, each auxiliary thyristor T0. 'f',,,'I゛. 1 or conductive state will be referred to as mode O, mode P, and mode Q, respectively. Next, we will explain the relationship between voltage and current in each mode. In mode P, the auxiliary winding 4b of the two sets of mutual reactors 4, 4'.

Winding Ob P l between each midpoint and one end of 4b, 0bp
)1, and from the condition of ampere-turn cancellation, i dl, i d2. i di, i″
d2 is not shown in Fig. 2 and is connected to two sets of three-phase bridge rectifier circuits 1 and 2.
The respective DC side output currents, Id, are DC load currents.

From equation (3), however, im = Am1d ---- (5) On the other hand, the electric current jJ2e d of the DC circuit 5 shown in Fig. 2 is ed = ed
a0edβ= e da” -Am -Vm -----
-(6) However, eda is the midpoint Oa of the main windings 4a and 4'a of the two sets of interphase reactors 4.4° shown in FIG.
eda is the voltage generated between the midpoint Oa of the main winding 4a and one end of the DC circuit 5 by the auxiliary circuit 7.

The other mode is mode 0. In the case of mode Q, in equation (4) and equation (6), the turns ratio Al11 according to equation (1) is
If O and Am are respectively set, the relational expressions for voltage and current in each mode can be obtained. And Q in the period when Vm>O
→O−+P mode transition and P→0→Q mode transition in the period of Vm<0, respectively, for the thyristor T.

, 'I' p + + T'' o + by natural commutation.

Current im and voltage edβ shown in equations (4) and (6)
are the current and voltage generated by applying the auxiliary circuit 7 shown in FIG. 2, and this is the AC side input current iu.

Helps reduce harmonics of iy and iw and pulsation of voltage ed in the DC circuit. This will be explained with reference to FIGS. 4 and 5.

Assuming that each operating mode O, P, and Q is the section shown in Fig. 2 (C), and the turns ratio A+n in equation (1) is approximately 0.3,
Said two sets of three-phase bridge rectifier concave-15 = DC side output currents idl, i'dl and id of paths 1 and 2
2 and i'd2 are constant smooth 1 as shown in Figure 4(a).
/2Id is superimposed with the pulsating portion im of amplitude Am'Id, resulting in an uneven waveform, and these idl, i'dl and id2
and i'd2 are distributed to each phase of the AC side input of the two sets of three-phase bridge rectifier circuits 1.2 by the thyristors T1 to 1゛1□, the AC side of the three-phase bridge rectifier circuit 1.2 Input U-phase current 1u++ 1. u2 has a step waveform as shown in FIG. 4(b), and the U-phase current iu of the three-phase AC circuit 3 is the sum of 1u4 and 1u2 (iu=i,
i, □), and as shown in FIG. 4(C), the waveform is equivalent to that of the 18-pulse method of the prior art. Similarly, 18-pulse waveforms are obtained for each part of the V-phase and W-phase current waveforms.

On the other hand, the main winding 4a of the two sets of interphase reactors 4, 4',
, 4'a, the voltage eda between the midpoints Oa and O'a has a sawtooth waveform including a 6f pulsation component as shown in FIGS. 2(a) and 5(a), or The DC circuit voltage e d (ed = e da+
e dl), which is not shown in FIG. 5(C), has a sawtooth waveform including a pulsation component of 18 f, and even in terms of pulsation reduction, the waveform is equivalent to the 18-pulse waveform of the prior art.

In this embodiment, the two sets of auxiliary windings 4b.

This is an example in which one tap is provided at the midpoint of 4b, or it is also possible to increase the number of pulses by increasing the number of taps. In addition, the description of this embodiment is based on each of the thyristors T1 to T, 2.
It is clear that the above effect can be obtained even when the control angle α is set to 6o[daql] or at other angles.

FIG. 6 is a circuit diagram showing an embodiment in which the power converter according to the present invention is applied to a self-excited rectifier and a tap is provided at the midpoint of the auxiliary winding. In FIG. 6, explanations that overlap with those in FIG. 2 will be omitted. A self-extinguishing element such as a GTO or a transistor, or a forced commutation thyristor is used for each switching element constituting the two sets of three-phase bridge conversion circuits 1.2 and the switching circuit 6, and the two sets of three-phase bridge conversion circuits 1. The switching element T of circuit 1.2 functions as a self-excited rectifier that can set the control angle α of T + to 1゛1□ to either lead or lag.

In view of the embodiments shown in FIGS. 2 and 6, the power conversion device according to the present invention replaces the DC load in the DC circuit 5 with a DC power supply, thereby producing a separately excited delayed reactive power supply device and a self-excited reactive power supply device shown in FIG. It is obvious that the present invention is applicable not only to a supply device but also to a separately excited inverter device or a self-excited inverter device (not shown in FIG. 8).

1. Effects of the Invention As specifically shown above with the embodiments, the present invention enables harmonics and harmonics of the AC side current equivalent to conventional multi-pulse generation without using a transformer and with a small number of switching elements. A power converter that has the effect of reducing DC side voltage pulsations can be obtained, and the power converter itself can be made smaller, 4-quantized, and lower in cost, as well as AC filters installed on the tributary side and DC side to reduce harmonics. Any DC filter for reducing current ripples can be made smaller and smaller in capacity, or can be made unnecessary. Further, by reducing the capacity of the DC filter, the coordination of the power conversion A position is also improved.

-1,9-1

[Brief explanation of the drawing]

FIG. 1 is a principle circuit diagram of a power conversion device according to the present invention;
FIG. 2 is a circuit diagram showing an embodiment of the power conversion device according to the present invention as a thyristor rectifier, FIGS. 3 to 5 are diagrams explaining the operation of FIG. 2, and FIG. A circuit diagram showing an embodiment, FIG. 7 is a circuit diagram without showing an embodiment as a separately excited delayed reactive power supply device, FIG. 8 is a circuit diagram showing an embodiment as a separately excited inverter device, and FIG. 9 10 is a circuit diagram of a conventional dual-three-phase Zyristor bridge 12-pulse rectifier, and FIG. 10 is an explanatory diagram of the operation of FIG. 9. In the drawings, 1.2 is a three-phase bridge conversion circuit, 3 is a three-phase AC circuit, 4.4'' is an interphase reactor, 5 is a DC circuit, 6 is an L7 conversion circuit, and 7 is an auxiliary circuit.

Claims (4)

[Claims] (1) The AC side ends of two three-phase bridge conversion circuits are connected in parallel, and the DC side positive and negative ends are each connected via the main winding of an interphase reactor equipped with an auxiliary winding having multiple taps. A double three-phase bridge power converter in which a DC circuit is connected between the midpoints of the main windings of the two interphase reactors, which is configured by a switching circuit using an auxiliary winding of each interphase reactor and an auxiliary switching element. A power conversion device characterized in that a double auxiliary circuit is inserted in series between the center point of the main winding of the interphase reactor at either the positive end or the negative end of the DC side and the DC circuit. (2) In claim 1, the AC side ends of two 3-phase bridge conversion circuits connected in parallel are connected to a 3-phase AC power supply, and the DC circuit consists of at least one of a DC reactor and a DC capacitor. The power conversion device is composed of a DC filter and a DC load, and is configured as either a separately excited type or a self-excited type rectifier for supplying power from the three-phase AC power source to the DC load. Power converter. (3) In claim 1, the AC open ends of two three-phase bridge conversion circuits connected in parallel are connected to a three-phase AC power supply, and the DC circuit is a DC circuit consisting of at least one of a DC reactor and a DC capacitor. Is it composed of a DC power source such as a filter and rectifier or storage battery?
Alternatively, the power conversion device is configured only with the DC filter, and is configured as either a separately excited type or a self-excited type reactive power supply device for supplying at least one of lagging or leading reactive power to the three-phase AC power source. A power conversion device characterized by: (4) In claim 1, the AC side ends of two 3-phase bridge exchange circuits connected in parallel are connected to either a 3-phase AC load or a 3-phase AC power supply, and the DC circuit is connected to a DC The power conversion device is configured with a DC filter consisting of at least one of a reactor and a DC capacitor, and a DC power source such as a rectifier and a storage battery, and the power conversion device supplies power from the DC power source to either the three-phase AC load or the three-phase AC power source. A power conversion device characterized in that it is configured as either a separately excited type or a self-excited type inverter device for performing.