JPS61221576A - High frequency modulation ac/dc converter - Google Patents

Abstract

PURPOSE:To reduce a harmonic current by providing a plurality of AC/DC converters, connecting the DC output sides of the converters in series, and shifting the phase of the modulated wave of converters at the prescribed angle, thereby decreasing the ripple component of the AC current. CONSTITUTION:Two sets of AC/DC converters CV1, CV2 have four GTOs T11-T14, T21-T24, and diodes D11-D14, D21-D24 connected in anti-parallel with the respective GTOs, and the DC output sides of the converters are connected in series. The gate ignition pulses of the converters CV1, CV2 are obtained by gate amplifiers 151, 152, respectively. The gate ignition pulses applied to the GTOs of the converters CV1, CV2 are displaced at a timing by a phase shifter 16.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a plurality of sets of AC/DC converters formed by bridge-connecting a unit arm of an antiparallel connection body of a semiconductor switching element having self-extinguishing ability and a diode. This relates to a high frequency modulation AC/DC converter 5A system.

(Technical background of the invention and its problems) As a rectifier circuit that converts AC FIl power into DC power,
The most common type is an uncontrolled rectifier circuit in which diodes are bridge-connected, but with the development of controllable semiconductor switching elements such as thyristors, controllable rectifier circuits have come into widespread use.

Here, the controllable type is a type that can adjust the output on average by controlling so that only a specific phase section of the conduction possible section is conductive, but when this control is implemented,
Cross 5! On the other hand, the problems of deterioration of power factor of electric power and increase of high frequency of alternating current are pointed out as drawbacks. In particular, when a heavy load is carried out intermittently, such as on road vehicles, and communication line cables such as telephone wires are laid along railway lines, it is necessary to remove high-frequency components for the purpose of improving the power factor of AC power and reducing inductive disturbances. It is hoped that this will be reduced.

In order to meet this demand, recently developed gate turn-off thyristors capable of high-power and high-speed switching (
An AC/DC converter using a high frequency pulse width modulation method (hereinafter referred to as GTO) is attracting attention as it has a high power factor and low frequency.

FIG. 3 shows the circuit configuration of this AC/DC converter.

The device shown in Fig. 3 is based on the circuit of an electric market, and the AC power collected by the collector PAN is transferred to the -th winding U.
-■ and a transformer TR having a secondary winding U-V and a reactor L to an AC/DC converter Cv, where it is converted to AC/DC and supplies DC power to a DC load LD. Note that a capacitor C is connected in parallel to the output end of the AC/DC converter CV. The AC/DC converter CV has a unit arm consisting of GTOT1 to T4 and diodes D1 to D4 connected in antiparallel, which are connected in a single-phase bridge. This circuit not only maintains the DC voltage at a constant value, but also performs 111 control so that the phase difference between the fundamental wave of the AC voltage and the AC current is eliminated, and also controls the AC current waveform to be as close to a sine wave as possible. have. In order to fulfill this function,
A reference value of the DC voltage is set by the setter 10, and this value is compared with the actual DC voltage value detected by the voltage detector VDD. This comparative deviation is multiplied by a multiplier 12 with an alternating current voltage detected by a voltage detector VD via a compensation stage 11 such as a delay circuit to create an alternating current reference. This reference value is compared with the actual alternating current value detected by the current transformer CT, and the comparison deviation is calculated from the harmonics of the triangular wave separately generated by the frequency generator 14 after passing through the second compensation stage 13. compare. The waveform in the center of FIG. 4 represents this comparison. The output after this comparison is distributed to each GTO by a logic circuit (not shown), amplified by the gate amplifier circuit 15, and turned on and off each GTO, thereby producing an output statement FIt as shown in the lower part of FIG. A current waveform is obtained. In the example in Figure 4, the modulation frequency is not that high compared to the frequency of the AC voltage in order to schematically represent the waveform, but in reality, by taking a high modulation frequency, the AC current waveform becomes more accurate. It becomes close to a good sine waveform.

By the way, since the DC output voltage of this type of AC/DC converter is generally determined by the withstand voltage value of the semiconductor element used in the converter, the DC voltage is limited by this. therefore,
In order to obtain higher DC voltage values, a common method is to connect a GTO and a diode in series.

On the other hand, one problem with the AC/DC converter shown in FIG.
As shown in the AC current waveform in the figure, the current waveform includes ripples due to the influence of the modulated wave, which causes harmonics to be generated. Therefore, if the modulation frequency is set infinitely high, the alternating current waveform becomes almost a sine wave.
Generally, the switching frequency of a GTO or the like is limited to a value of about 1 llz or 2 H 2 from the viewpoint of heat generation due to switching loss.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and
It is an object of the present invention to provide a high frequency modulation type AC/DC converter that can reduce ripples in the li current waveform to reduce harmonic components and obtain a high DC output voltage.

(Summary of the Invention) In order to achieve the above object, the present invention comprises a transformer having a plurality of secondary windings, and an anti-parallel connection body of a semiconductor switching element and a diode, each having a self-extinguishing ability, as a unit arm. a plurality of sets of AC/DC converters in bridge connection, each AC input side connected to a separate secondary winding of the transformer, and each DC output side connected in series; and AC input voltage of each AC/DC converter. is modulated by a high-frequency modulated wave consisting of a triangular wave having a predetermined phase difference between the AC/DC converters to make the AC current flowing through each secondary winding of the transformer into a sine wave shape, and to eliminate ripple components contained in each AC current. The present invention is characterized by comprising a control circuit that turns on and off the semiconductor switching elements of each of the AC/DC converters so that they cancel each other out with the transformer.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the present invention.

This embodiment assumes the main circuit of an electric vehicle as in the case of FIG. 3. However, the transformer TR used in this embodiment has two sets of secondary windings u1-v1 and LJ2-V2, and correspondingly two sets of AC/DC converters C1 and C
Equipped with V2. Both vehicles direct converter CV1. The circuit configuration of CV2 itself is the same as that in Figure 3, and each
GTO711~T14, T21~T24 and individual G
Four diodes D connected in antiparallel to TO
11-D14. It consists of D21 to D24. The secondary windings u1 to ■1 are connected to the AC input side of the AC/DC converter C■1 via the reactor L1, and the secondary windings u2 to v2 are connected to the AC input side of the AC/DC converter CV2 via the reactor L2. Both vehicle direct converters CV1. Capacitors C1 and C2 are connected in parallel to the DC output side of CV2, and are connected in series with each other to supply DC power to the DC load LD.

Each AC/DC converter CV1. The control section of CV2 is basically the third
It has the same configuration as the one in the figure, and has a voltage reference set by a common setting device 10 and voltage detectors VDD1. V.D.
The output DC voltage of each AC/DC converter detected by D2 is compared, and the comparison deviation is calculated by the first compensation stage 111, 112.
, for example, is inputted to one input terminal of the multipliers 121 and 122 via a delay circuit. The other input terminals of the multipliers 121 and 122 receive the AC voltage detected by the voltage detector VD1. Multipliers 121 and 122 respectively multiply both input voltage values and generate AC'! 11 current reference is made, the AC current reference is compared with the actual AC current value detected by the current transformer CT1°C70, and the deviation is passed through the second compensation stage 131 and 132, and then the modulated wave is generated. The gate amplifier circuit 1 for the first AC/DC converter CVI uses the comparison deviation obtained by direct comparison with the triangular modulated wave separately generated by the device 14.
51, and the modulated wave is transmitted to 9 by a phase shift circuit 16.
The comparison deviation obtained by comparing the modulated wave obtained by shifting in the 0@ delay direction (see Figure 2) is transferred to the second AC/DC converter CV.
By using such a modulated wave, the G of each AC/DC converter CV1, CV2 is
The gate ignition pulses applied to the TO are also shifted from time to time, and as a result, as shown in the waveforms of AC current 1 and AC current 2 in Figure 2, harmonics of the input currents of each AC/DC converter are generated. The ripple components will cancel each other out.

The alternating currents synthesized by the transformer TR end up as shown in the bottom row of Figure 2, with characteristics equivalently similar to those obtained when one AC/DC converter is operated at a higher modulation frequency. The ripple component of alternating current can be reduced.

In the above embodiment, a case has been described in which the secondary sides of two sets of AC/DC converters are connected in series, but if it is desired to obtain an even higher DC voltage, more AC/DC converters may be connected in series. In that case, the phase difference between each AC/DC converter of the triangular wave may be 180°/n depending on the number n of converters. For example, the phase difference when n-3 is 60°, and when n-4
If it is set to 45 degrees, the most efficient ripple reduction effect can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, by providing a plurality of AC/DC converters, connecting their DC output sides in series, and shifting the phase of the modulated wave of each converter circuit by a certain angle, the ripple of the AC current can be reduced. It is possible to reduce the harmonic current by reducing the amount of current, and also to obtain a high DC voltage. This harmonic component reduction effect is a remarkable effect that cannot be obtained by simply connecting GTO and diodes, which are the components of a single converter circuit, in series for each arm using a single converter circuit in order to obtain a high DC voltage. .

[Brief explanation of the drawing]

FIG. 1 is a circuit connection diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram of voltage and current waveforms of the device shown in FIG. 1, FIG. 3 is a circuit connection diagram of a conventionally known AC/DC converter, and FIG. FIG. 4 is an explanatory diagram of voltage and current waveforms of the device of FIG. 3. TR...Transformer, CVI, CV2...AC/DC converter,
T11-T14. T21-T24...Gate turn-off thyristor, 011-014.021-D24...
Diode, LD...DC load, 10...setting device,
voi, VDDl, VDD2...voltage detector, CT1
．． CT2...Current transformer, 14...Modulated wave generator, 15
1.152...Gate amplifier circuit, 16...Phase shift circuit. Applicant's agent Inomata

Claims (1)

[Claims] A transformer having a plurality of secondary windings, an inverse parallel connection body of a semiconductor switching element and a diode, each having a self-extinguishing ability, are bridge-connected as a unit arm, and each AC input side are connected to separate secondary windings of the transformer, and each set of AC/DC converters is connected in series with each DC output side. The alternating current flowing through each secondary winding of the transformer is modulated with a high-frequency modulated wave consisting of a triangular wave having a sine wave shape, and the ripple components contained in each alternating current cancel each other out in the transformer. An AC/DC converter comprising: a control circuit that controls on/off of semiconductor switching elements of each of the AC/DC converters.