JPH01259759A - Power conversion device - Google Patents

Abstract

PURPOSE:To reduce low-order higher harmonics, by magnetically coupling each reactor connected to a plurality of the secondary windings of a transformer respectively and by forming them so that the sense and the size of the coupling may mutually be negated. CONSTITUTION:In a power conversion device the primary winding P of a transformer TR is connected to a current collector PAN, the other end of which is earthed through a wheel GB. This transformer TR is equipped with secondary windings S1-4 each having inductances SL1-4. To each secondary winding S1-4 the AC input terminals of converters CONV14 are connected through each reactor ACL 1-4. The converter CONV1 is constituted in a single phase bridge circuit with GTO G11-4, etc. Other converters CONV2-4 are constituted in the same way, from which the power is supplied to a load induction motor IM. On this occasion, sum of the inductance values of the reactor and the secondary winding are equalized respectively. The fundamental wave and ripple portion of the AC input terminals of the converter CONV can thereby be same in size.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is used as a power source for driving a drive motor for dual use in railways as a load, and the diodes are connected to each other. The same number of bridges as the secondary windings are constructed using controlled rectifying elements connected in antiparallel.The AC input side of each bridge is connected to the secondary winding via a reactor, and the DC output side of each bridge is connected to each other. The present invention relates to an improvement in a power conversion device that is connected in parallel to a load together with a capacitor, and each bridge is pulse width modulated 60 (PWM).

(Prior Art) FIG. 3 is a circuit diagram showing an example of a conventional power conversion device, in which one end of the primary winding P of the transformer TR is connected to the current collector PAN, and fl! l! The end is grounded via wheel CB. Transformer TR has inductance SLI, SL2
．． SL3. Secondary windings 31. each having an SL4.
S2. S3. S4, and each secondary winding 81 to S4
reactors ACLI, ACL2. ACL3
．． TE converter C0NV 1 , CoN via ACL4
V2.

C0NV3. The AC input terminal of C0NV4 is connected.

Converter C0NVI is a gate turn-off thyristor (hereinafter referred to as GTO thyristor) Gll.

G12. G13. G14, diode D11°C12
, C13, and C14 are each constituted by a single-phase bridge circuit connected in antiparallel. converter C0NV2
．． C0NV3. Similarly, for C0NV4, diode D21
~D24 and GTO thyristors 021~G24, diodes D31~D34 and GTO thyristors 031~G34,
Diodes D41~D44 and GTO thyristor G41~
G44.

The DC output terminals of the converters CONV1 to C0NV4 are connected in parallel with each other, and are connected to a capacitor CO, which is generally called a smoothing capacitor.The input terminal of the inverter INV is connected to this capacitor CO, and the output terminal 1 of the inverter INV is connected to the capacitor CO, which is generally called a smoothing capacitor. An induction electric motor (ii I M) as this load is connected to.

In the configuration as described above, single-phase AC power taken in from the current collector PAN is transformed by the transformer TR and inputted to the converters C0NVI to C0NV4. Inductance 5 of secondary windings 81 to S4 of transformer TR
The short circuit current is suppressed by LI-ysL4 and the inductance of reactors ACLI to ACL4.

GTO thyristor G11-G14 of converter CON■1-CoNV4.021-G24, G31-G34, G
41 to G44 are controlled by a control circuit (not shown) to keep the voltage across the capacitor CO constant.
As a result, single-phase AC power is converted to constant voltage DC power and input to the inverter INV.

By switching the GTO thyristor using the PWM $ control signal, the power converter with this configuration can increase the input power factor compared to a phase control converter, and can perform control with fewer harmonics. It has characteristics. In particular, each converter C0NVI~
By shifting the phases of the modulated triangular waves used for PWM control of C0NV4, harmonics of the primary current of transformer TR can be further reduced.

Inductances SLI to SL4 of secondary windings 81 to S4 of transformers TR connected to AC input terminals of converters C0NV1 to C0NV4 and reactors ACL1 to -A
The inductance of CL4 needs to suppress the rate of change of current when controlling PWX1, and therefore plays an important role.

The AC input current waveform of converters C0NV1 to C0NV4 is a waveform in which a triangular ripple component is superimposed on a sine wave current with the same fundamental frequency as the AC power supply frequency, as shown by the solid line or broken line in Fig. 4. The size of the wave current is determined by the size of the load, and the size of the ripple component is determined by the size of the inductance connected to the AC input terminal of converters CON■1 to C0NV4 and the frequency of the modulated triangular wave used for PWM control. It will be done.

Therefore, the ripple component is suppressed and the peak current is
4.041~G44 maximum? I! It is necessary to provide the AC input terminals of converters C0NVI to C0NV4 with a sufficiently large inductance to keep the IrTX current or lower.

Furthermore, when converters C0Nv1 to C0NV4 are operated with the phase of the modulated triangular wave shifted, the AC input current waveform is
For example, for converter C0NVI, the waveform is shown by the solid line in Figure 4, and for converter C0NV2, the waveform is shown by the broken line in Figure 4, and for converter C0NVI, the waveform is shown by the broken line in Figure 4.
V3. Regarding CON24, the waveform has a ripple phase between the solid line and the broken line in FIG. 4. In this case, the main ripple frequency component seen in the primary t& current of the transformer TR can be four times the ripple frequency of the input current of each converter C0NV1 to C0NV4,
Low-order harmonics can be removed even at relatively low modulation frequencies.

However, the above features apply to each converter C0NV1 to C0N.
It is a necessary condition that the magnitude of the current of V4, especially the magnitude of the ripple component, match each other.

Therefore, the inductances present at the AC input terminals of the converters CONV1 to C0NV4 must be equal to each other, that is, the inductances SLI present in the secondary windings 81 to S4 of the transformer TR, respectively, must be equal to each other.
The inductance value of ~SL4 is tsl ~t84, and the inductance of reactors ACL1~ACL4 is
When tL, ~'-L4, tSl''j+, 1:t
S2 +tL2""ts5+tL3"ts4"tI-4
It is necessary that

(Problem to be solved by the invention) However, when this power conversion device is installed in a railway vehicle, for example, where space is limited, it is necessary to reduce the size and weight of the entire device. It is necessary to make the TR smaller and lighter.

For this reason, it is difficult to manufacture the secondary windings 81 to 84 without coupling them, and each of the secondary windings S1 to S
It is also difficult to match the inductance values of No. 4. In addition, in the past, the same reactors ACLI to ACL4 were used, so each = 77 i < -9CON
An imbalance occurs in the current between V1 and CON V4,
There is a problem that the harmonic reduction feature cannot be fully utilized.6 Furthermore, due to the phase difference corresponding to the ripple of the AC input current of the converters C0NV1 to C0NV4, the secondary windings 81 to 8
The equivalent inductance of each of the considered secondary windings 81 to S4 changes, including the coupling between the two, and as a result, the ripple component of the AC input current increases compared to when operating without a phase difference. There was a problem with that.

The present invention aims to provide a power conversion device that can ensure current balance between converters of tI number without increasing the size of the transformer, and can reliably take measures against low-order harmonics.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a primary winding connected to an AC power supply, each having a different inductance value, and magnetically coupled to each other. A transformer has a plurality of secondary windings and transforms an AC power supply voltage, a converter is connected to each secondary winding of the transformer and is controlled by pulse width modulation, and the AC power of each converter is controlled by pulse width modulation. In a power conversion device including a reactor connected between an input end and each of the secondary windings, the inductance value of the reactor connected to the AC input end of each converter and each secondary winding of the transformer are The reactor is configured so that the sum of inductance values in the lines is equal at the AC input terminal of each converter.

(Function) With this configuration, current balance between multiple converters can be ensured without increasing the size of the transformer.
Measures against low-order harmonics can be taken reliably.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a schematic circuit diagram for explaining the present invention in detail. The converter is C0NV1. I am listing the 2-bridge configuration of C0NV2. The inductance SLI of the secondary windings SL and S2 of the transformer TR, respectively,
The inductance values of SL2 are t, 1 and t3, respectively.
2 (where ts+ >ts2), the mutual inductance of both is m, the inductance values of reactors ACLI and ACL2 are tLl, tL2, and the mutual inductance of both is M. At this time, ts1+tL1 ” tS2 +LL2 Furthermore, m=-
M, and is configured to cancel the effects of magnetic coupling between the secondary windings 31 and S2 of the transformer TR and between the reactors ACLL and ACL2.

Now, in such a configuration, converter C0N
The relationship between the voltage and current of the circuit at the AC input terminal of VI and coNv2 is as follows. The induced voltage in the secondary winding isi of the transformer TH is vsl, the current is iSl, and the converter C0N
Let the AC human power eA Wb pressure of V1 be ・υc1. Also, the induced voltage of the secondary winding S2 is υ82, and the current is 18
2. The AC input terminal voltage of converter CON V 2 is vc
2. In this case, the following equation holds true for each AC circuit.

Here, tS1+LL, +=ts2"k2"'■, and the value is t. , and if M=m, the above equations (1) and (2) become as follows, and the inductances of each AC circuit become equal to each other. Moreover, the magnetic influence of other windings is canceled, and the influence of the phase difference of the modulated triangular wave of PWM control can be eliminated.

FIG. 2 is a circuit diagram showing an embodiment using the principle of the present invention described above, and the same parts as in FIG. Secondary winding 31 of transformer TR,
32. S3, 34 interface SLI, SL2.
SL3. Inductance value tdi of SL4, A82
r A83 T A84 is ls+ >ts21
ts5 > tsa, and the secondary winding S of transformer TR
The mutual inductance between the secondary windings S3 and 82 is m12, the mutual inductance between the secondary windings S3 and 84 is m34, and the reactor A CL 1 .

ACL2. ACL3. The inductance value of ACL4 is set to 1. , ・t[,2r z, 61 lL4 ・Mutual inductance: A12 is set between reactors ACLI and ACL2, and between reactors ACL3 and ACL4
A mutual inductance of 1v134 is provided between them.

At this time, zs++zt, +°ts2+tL, 2=ts5+LL5
= ts4''L, 4, and the mutual inductance is
m, 2 = - ~ L + 2 - m3a = M so that the magnetic coupling between the secondary windings 81 to 84 of the transformer TR and the reactors ACL1 to ACL4 are mutually canceled.
34=I do.

By configuring as above, converter C0NV
The inductance connected to the AC input terminal of 1 to C0NV4 is the inductance SLI to SL4 of the secondary winding 81 to S4 of the transformer TR and the reactor ACLI to ACL4.
When considered together, they become equal.

Therefore, the fundamental wave and ripple components at the AC input terminals of the converters CoNv1 to C0NV4 can be made to have the same magnitude.

Moreover, the influence of coupling between the secondary windings 81 to 84 of the transformer TR can be removed. Therefore, even if PWM control is applied to each converter C0NV1 to CONV4 by giving a phase difference to the modulated triangular wave, the ripple component of the AC input current will be about the same size as when no phase difference is given to the modulated triangular wave. .

According to the embodiment of the present invention described above, the reactors A each connected to the a number of secondary windings 81 to S4 of the transformer TR.
CLI to ACL4 are magnetically coupled to each other, and the direction and magnitude of the coupling are set so as to cancel out the coupling between the secondary windings 81 to 54, thereby reducing the size of the transformer TR. It is possible to reduce the next harmonic.

[Effects of the Invention] According to the present invention described above, it is possible to provide a power conversion device that can ensure current balance among a plurality of converters and reliably take measures against low-order harmonics without increasing the size of the transformer. can.

[Brief explanation of the drawing]

FIG. 1 is a schematic circuit diagram for explaining the principle of the power conversion device of the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the present invention.
Figure 3 is a circuit diagram showing an example of a conventional power conversion device;
The figure is a diagram showing an example of the AC input current waveform of the converter. PAN...Current collector, TR...Transformer, ACLL. ACL2. ACL3. ACL4...Reactor, C0
NVI, C0NV2. C0NV3. C0NV4...Converter, CO...Capacitor, INV...Inverter, IM...Induction motor. Applicant's agent Patent attorney Takehiko Suzue------
---Ko

Claims (1)

[Claims] A primary winding connected to an alternating current power supply and a plurality of secondary windings each having a different inductance value and magnetically coupled to each other, and transforming the alternating current power supply voltage. a transformer, a pulse width modulation controlled converter connected to each secondary winding of the transformer, and a reactor connected between an AC input terminal of each converter and each of the secondary windings; In the power conversion device, the sum of the inductance value of the reactor connected to the AC input terminal of each of the converters and the inductance value of each secondary winding of the transformer is equal for each converter. A power conversion device characterized in that the reactor is configured as follows.