JPH06217559A - Power converter - Google Patents

Abstract

PURPOSE:To suppress the asymmetrical magnetization of a transformer caused by a DC component contained in the alternating current side of a power converter. CONSTITUTION:A saturable reactor 4 and reactor having an exciting characteristic proportional to the number of interlinked flux are connected in series with the primary side of a transformer 3. When a DC voltage is generated in the transformer 3, an asymmetrical magnetization control circuit 8 detects a DC component proportional to the number of interlinked flux from the exciting current flowing to the reactors 4 and 5 and suppresses the asymmetrical magnetization of the transformer 3 by correcting an output voltage feedback signal. Therefore, the occurrence of unstable phenomena caused by overcompensation is nearly completely eliminated and the gain tolerance of a control system can be remarkably widened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power conversion device that reversely or forwardly converts electric power, and relates to suppression of a direct current component contained on the alternating current side thereof.

[0002]

2. Description of the Related Art A conventional DC component compensating circuit for a power converter detects a DC component contained on the AC side by a reactor having a non-linear excitation characteristic, as described in Japanese Patent Laid-Open No. 2-307374. .

[0003]

In the above-mentioned prior art, the saturation characteristic of the reactor is utilized to detect the DC component contained in the AC side of the power converter, but the exciting current when the reactor is saturated is a chain. Since it increases more than proportional to the number of magnetic fluxes, there is a problem that the gain of the control system rapidly increases equivalently and overcontrol is likely to occur.

An object of the present invention is to detect a DC component contained on the AC side of a power conversion device in an amount proportional to the number of interlinkage magnetic fluxes of the reactor, and to stably control without overcontrol.

[0005]

In order to solve the above problems, a plurality of reactors having different magnetic saturation characteristics are connected in series,
This is achieved by connecting in parallel or series-parallel connection to the AC side of the power converter in parallel to detect the DC component contained in the AC side and adding it to the signal generator in the control circuit.

[0006]

When the DC component is generated on the AC side of the power conversion device due to the offset in the control circuit or the variation of ON / OFF of the self-extinguishing element in the main circuit, the saturable reactor is saturated, but the flux linkage Since a reactor that supplies a proportional exciting current can detect a DC component proportional to the magnetic saturation amount,
Stable control can be performed without overcontrol.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. The main circuit 100 includes a DC voltage source 1, an inverter 2 and a transformer 3, and converts DC power into AC power. The control circuit 101 has the following configuration. A series connection of a saturable reactor 4 and a reactor 5 for flowing an exciting current proportional to the number of flux linkages is connected in parallel with the transformer 3, and the current detector 6 detects the exciting current flowing through the reactors 4, 5. Then, the output voltage of the transformer 3 and the output signal of the current detector 6 are calculated by the adder 7, and the bias magnetic control circuit 8
To enter. This output and the output signal of the signal generator 9 are calculated by the adder 10, and this output is given to the inverter control circuit 11 which drives the inverter 2 to drive the inverter 2. Here, the saturable reactor 4, the reactor 5, the current detector 6, and the bias magnetic control circuit 8 are circuits provided to suppress the bias magnetization of the transformer 3.

1 (2) and FIG. 2 to FIG.
The operation of the bias magnetic control circuit 8 shown in (1) will be described in detail. As shown in FIG. 1B, the bias magnetic control circuit 8 is composed of a dead zone formed by the diodes 12 and 13 and an integrator 14. 2 (1) is an excitation characteristic of the saturable reactor 4 and the reactor 5, and FIG. 2 (2) is an excitation characteristic of the saturable reactor 4 and the reactor 5 connected in series.
(3) shows the excitation characteristic of the transformer 3 and the characteristic of FIG. As shown in FIG. 2 (1), the saturable reactor 4 saturates at the flux linkage number φ ₁ or more, and the reactor 5 does not saturate until the flux linkage number φ ₂ . By connecting two reactors having different characteristics in series, the characteristics shown in FIG. 2B can be obtained. Further, as shown in FIG. 2C, the excitation characteristic due to the series connection of the saturable reactor 4 and the reactor 5 is saturated first with respect to the transformer 3, and the inclination at the time of saturation is proportional to the transformer 3. It has characteristics. As a result, the exciting current increases in proportion to the number of interlinkage magnetic fluxes in the saturation region, so that by detecting this, an amount proportional to the amount of magnetic bias of the transformer 3 can be detected.

3 and 4 show the excitation characteristics of the saturable reactor 4 and the reactor 5 connected in series. FIG. 3 shows the excitation characteristic when the primary side AC voltage of the transformer 3 does not include the direct current component, and FIG. 4 shows the excitation characteristic when the direct current component includes the direct current component. In FIG. 3, the saturable reactor 4,
A positive / negative symmetrical current flows through the reactor 5, and if this current is made equal to the voltage drop due to the diodes 12 and 13 in FIG. 1 (2), no direct current component is generated in the output of the integrator 14. However, when the primary side of the transformer 3 contains a DC component as shown in FIG. 4, the saturable reactor 4 and the reactor 5 are connected.
The excitation characteristic due to the series connection with and is biased in either the positive or negative direction of the magnetic flux. Then, the currents of the saturable reactor 4 and the reactor 5 become positive and negative asymmetrical, and only the peak value of this current is detected in the dead zone by the diodes 12 and 13,
The integrator 14 detects a DC component proportional to the number of flux linkages.
Due to this DC component, the output voltage feedback signal of the transformer 3 is corrected, and the magnetic bias of the transformer 3 can be suppressed.

Further, according to the present invention, as shown in FIGS.
It can also be realized by connecting reactors having different characteristics in parallel on the AC side or connecting a plurality of reactors connected in series with an AC power source in parallel. Here, FIG. 5 and FIG.
The connection 103 of the reactor of (1) is replaced.

In FIG. 5, a saturable reactor 15 is connected in parallel to the primary side of the transformer 3, and a current detector 17 is connected to the connection line.
, The reactor 16 is connected in parallel, and the current detector 18 is attached to the connection line.
The output signals of 7 and 18 are combined by the adder 19 and the arithmetic unit 2
The waveform is shaped at 0 and supplied to the adder 7 to correct the output voltage feedback signal of the transformer 3. The output of the adder 19 is obtained by adding the currents of the saturable reactor 15 and the reactor 16, which can obtain the same characteristics as the current obtained by connecting the reactors 15 and 16 in series. Output has the same characteristics as in FIG.

Further, in FIG. 6, a plurality of reactors having different characteristics connected in series on the AC side are connected in parallel, and the detection signal can have a characteristic closer to the excitation characteristic of the transformer 3. This is because a saturable reactor 21 and a reactor 23, which have different characteristics from each other, are connected in series and a saturable reactor 22 and a reactor 24 are connected in series, and a current flowing through each of them is detected by a current detector 2.
5 and 26, combine by adder 27, form waveform by calculator 28, and bring it closer to the excitation characteristic of transformer 3.

Further, the present invention can be applied not only to the inverse converter but also to the forward converter. FIG. 7 shows an example applied to the converter device. Main circuit is AC voltage source 29 and converter 3
It consists of 0. The control circuit has the following configuration. The input current is detected by the current detector 34, and the saturable reactor 31 and the reactor 32 that flows an exciting current proportional to the number of flux linkages connected in series are connected in parallel with the AC voltage source 29. The exciting current flowing through the reactors 31 and 32 is detected. This value and the output of the current detector 34 are combined by an adder 35, and the output of the bias magnetic control circuit 36 for suppressing the bias magnetization of the transformer on the power supply side, the output of the bias magnetic control circuit 36 and the signal generator. It is composed of an adder 38 for synthesizing the output of 37 and a converter control circuit 39 for driving a converter by the output of the adder 38. Here, even if a direct current component is generated in the converter, the direct current component can be suppressed by the above circuit configuration, and the magnetic bias of the transformer on the power supply side can be prevented.

[0014]

As described above, according to the present invention, in a power conversion device that reversely or forward converts electric power, a plurality of reactors having different magnetic saturation characteristics are used to detect a direct current component proportional to the magnetic saturation amount and perform overcontrol. Control can be performed stably, and even if there are relatively large variations in the manufacturing of the reactor, the control works well, and the allowable range of the gain of the control system can be made much wider.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment when the present invention is applied to an inverter device.

FIG. 2 is an excitation characteristic diagram of a reactor.

FIG. 3 is an excitation characteristic diagram of the saturable reactor 4 and the reactor 5 connected in series when the primary side AC voltage of the transformer 3 does not include a DC component.

FIG. 4 is an excitation characteristic diagram of the saturable reactor 4 and the reactor 5 connected in series when the primary side AC voltage of the transformer 3 includes a DC component.

FIG. 5 is a diagram showing an example in which reactors having different characteristics are connected in parallel.

FIG. 6 is a diagram showing an example in which reactors having different characteristics are connected in series and parallel.

FIG. 7 is a diagram showing an embodiment when the present invention is applied to a converter device.

[Explanation of symbols]

1 ... DC voltage source, 2 ... Inverter, 3 ... Transformer, 4 ... Saturable reactor, 5 ... Reactor, 6 ... Current detector, 7
... adder, 8 ... bias magnetic control circuit, 9 ... signal generator, 10 ...
Adder, 11 ... Inverter control circuit, 12, 13 ... Diode, 14 ... Integrator, 15 ... Saturable reactor, 16
... reactor, 17, 18 ... current detector, 19 ... adder, 20 ... calculator, 21, 22 ... saturable reactor, 2
3, 24 ... Reactor, 25, 26 ... Current detector, 27
... adder, 28 ... arithmetic unit, 29 ... AC voltage source, 30 ... converter, 31 ... saturable reactor, 32 ... reactor, 33, 34 ... current detector, 35 ... adder, 36 ... bias magnetic control circuit, 37 ... Signal generator, 38 ... Adder, 39 ...
Converter control circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Seki 3-2-1, Sachimachi, Hitachi City, Ibaraki Prefecture Inside Hitachi Engineering Co., Ltd.

Claims (3)

[Claims] 1. A power converter comprising a main circuit including at least one of a forward converter for converting AC to DC and an inverse converter for converting DC to AC, and a control circuit having a function of generating a reference signal wave. In, in which a plurality of reactors having different characteristics are connected in series is provided on the AC side of the forward converter or the inverse converter, and the output signal of the current detector attached to the connection line is added to the AC side voltage feedback signal An electric power converter that supplies a control circuit and suppresses a direct current component superimposed on an alternating current side. 2. The device according to claim 1, wherein a plurality of reactors having different characteristics are connected in parallel, and the reactor is provided on the alternating current side of a forward converter or an inverse converter, and a current detector is attached to the connecting wire.
A power conversion device characterized by suppressing a direct current component superimposed on an alternating current side. 3. The method according to claim 1, wherein a plurality of reactors having different characteristics are connected in series and parallel to each other, and the reactor is provided on the AC side of a forward converter or an inverse converter, and a current detector is attached to the connection line to superimpose on the AC side. A power converter that suppresses the generated direct current component.