JP2010110179A - Rectifying circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rectifying circuit which is controlled based on the same control logic even when the circuit is applied to a three-phase AC power supply and a single-phase AC power supply. <P>SOLUTION: The rectifying circuit 1 has a full-wave rectifying circuit 13 connected to the output side of each phase of the three-phase AC power supply 11 through reactors 12a, 12b, 12c, and two electrolytic capacitors 14a, 14b connected between the output terminals of the full-wave rectifying circuit 13. The two electrolytic capacitors 14a, 14b are connected in series. A connection point of the two electrolytic capacitors 14a, 14b and a neutral point N of the three-phase AC power supply 11 are connected. The input sides of each phase of the full-wave rectifying circuit 13 and the connection point C of the electrolytic capacitors 14a, 14b, are connected through first switching elements 16a, 16b, 16c. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rectifier circuit.

Conventionally, a rectifier circuit including an active power factor correction circuit is known. FIG. 6 shows a configuration example of a rectifier circuit including an active power factor correction circuit applied to a single-phase AC power supply. In this type of rectifier circuit, high-efficiency power supply is realized by driving the switch S1 at high speed.
Further, for example, Patent Document 1 discloses a rectifier circuit applied to a three-phase AC power source as shown in FIG. Specifically, Patent Document 1 discloses a rectifier circuit in which input terminals of a three-phase diode full-wave rectifier circuit 102 and connection points of smoothing capacitors C101 and C102 are connected via bidirectional switches S101, S102, and S103. Is disclosed. In this rectifier circuit, a zero-cross point of the three-phase AC voltage is detected, and a control signal is output to turn on the bidirectional switch of the corresponding phase based on this zero-cross, so that one cycle is constituted by a voltage waveform of 12 steps. To be.
Japanese Patent No. 3422218

  By the way, in the rectifier circuit disclosed in Patent Document 1 (see FIG. 7), the input current waveform (here, one arbitrary phase is selected) input to the three-phase diode full-wave rectifier circuit is: The waveform is as shown in FIG. Further, in the rectifier circuit applied to the single-phase AC power source shown in FIG. 6, the input current waveform input to the full-wave rectifier circuit is a waveform as shown in FIG. These input current waveforms show waveforms when the switching elements included in the respective rectifier circuits are opened.

  As described above, in the rectifier circuit shown in FIG. 7 disclosed in Patent Document 1, the AC current waveform of each phase (see FIG. 8) input to the full-wave rectifier circuit is applied to the single-phase AC power supply. Since it is different from the input current waveform (see FIG. 9) of the full-wave rectifier circuit in the rectifier circuit, different control logics have to be assembled for single-phase and three-phase AC, requiring labor. .

  The present invention has been made to solve the above-described problem, and is a rectifier circuit that can be controlled based on the same control logic when applied to a three-phase AC power source and when applied to a single-phase AC power source. The purpose is to provide.

In order to solve the above problems, the present invention employs the following means.
The present invention comprises a full-wave rectifier circuit connected via a reactor to the output side of each phase of a three-phase AC power supply, and a plurality of capacitors connected between output terminals of the full-wave rectifier circuit, The capacitors are connected to each other in series, and any one of the connection points of the capacitors and a neutral point of the three-phase AC power supply are connected. Either one of the input terminal of each phase of the full-wave rectifier circuit and the capacitor Provided is a rectifier circuit connected to a connection point via a first switching element.

According to such a configuration, since any one of the connection points of the capacitors and the neutral point of the three-phase AC power supply are connected, the current waveform input to the full-wave rectifier circuit is shown in FIG. Waveform, that is, almost the same as when applied to a single-phase AC power source.
Thereby, even when applied to a three-phase AC power supply, it is possible to control the on / off of the first switching element corresponding to each phase according to the same control logic as in the case of a single-phase AC power supply. As a result, the single-phase harmonic technology can be directly applied to the three-phase AC power source, and the labor required for developing the control logic can be reduced.

  In the rectifier circuit, when any one of the connection points of the capacitors and the neutral point of the three-phase AC power supply are connected via a second switching element, the load is equal to or less than a predetermined threshold value. In addition, the first switching element and the second switching element may be turned off, and the second switching element may be turned on when the load exceeds the threshold value.

  As described above, when the load is equal to or lower than the threshold value, the first switching element and the second switching element are turned off, so that power loss due to switching can be suppressed. As a result, efficiency can be improved.

  According to the present invention, there is an effect that control can be performed based on the same control logic when applied to a three-phase AC power source and when applied to a single-phase AC power source.

Hereinafter, an embodiment of a rectifier circuit according to the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a block diagram showing a schematic configuration of a rectifier circuit according to the first embodiment according to the present embodiment. As shown in FIG. 1, the rectifier circuit 1 according to this embodiment includes a full-wave rectifier circuit 13 connected to the output side of each phase of a three-phase AC power supply 11 via reactors 12a, 12b, and 12c. Two electrolytic capacitors 14 a and 14 b connected between the output terminals of the rectifier circuit 13 are provided. The two electrolytic capacitors 14a and 14b have, for example, the same capacitance and are connected in series. A load 15 is connected between the output terminals of the full-wave rectifier circuit 13.

Further, in the rectifier circuit 1, the neutral point N of the three-phase AC power supply 11 and the connection point C of the electrolytic capacitors 14a and 14b are connected, and the input side of each phase of the full-wave rectifier circuit 13 and the electrolytic capacitor 14a. , 14b are connected to each other via first switching elements 16a, 16b, 16c.
Specifically, the neutral point N of the three-phase AC power supply 11 and the connection point C of the electrolytic capacitors 14a and 14b are connected by a connection line L1. Further, input terminals corresponding to the respective phases of the full-wave rectifier circuit 13 are connected to the connection line L1 via the first switching elements 16a, 16b, and 16c.

  The voltage zero cross point of the three-phase AC power supply 11 is detected by the zero cross detector 17 and output to the controller 20. A current flowing in any one phase of the three-phase AC power supply 11 is detected by the current detection unit 18 and output to the control unit 20 as a load current. In addition, the output voltage of the full-wave rectifier circuit 13 is detected by the DC voltage detector 19 and output to the controller 20. The control unit 20 controls on / off of the first switching elements 16a, 16b, and 16c based on the input information.

Here, FIG. 2 shows an input current waveform (select one phase arbitrarily) of the full-wave rectifier circuit 13 when the first switching elements 16a, 16b, and 16c are turned off. In FIG. 2, the horizontal axis represents time, and the vertical axis represents the current value. As shown in FIG. 2, in the rectifier circuit 1 according to the present embodiment, the current waveform input to the full-wave rectifier circuit 13 is almost the same as the input current waveform when applied to the single-phase AC power source shown in FIG. I understand that there is no.
Thereby, even when applied to a three-phase AC power supply, it is possible to control the on / off of the first switching element corresponding to each phase according to the same control logic as that applied to a single-phase AC power supply. .

  FIG. 3 shows an example of harmonic components of the input current of the full-wave rectifier circuit 13 when the rectifier circuit according to this embodiment is employed. In FIG. 3, the horizontal axis indicates the order of the high frequency component, and the vertical axis indicates the current value. As shown in FIG. 3, it can be seen that the level of the harmonic component contained in the input current is low and is below the IEC standard value in all orders.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG.
The rectifier circuit according to the present embodiment is connected to the connection line L1 that connects the neutral point N of the three-phase AC power supply 11 and the connection point C of the electrolytic capacitors 14a and 14b in the rectifier circuit according to the first embodiment described above. Two switching elements 30 are provided.
In FIG. 4, the second switching element 30 is provided on the connection line L1 on the three-phase AC power supply side with respect to the connection point of the switching elements 16a, 16b, and 16c, but is not limited to this arrangement. You may provide in the electrolytic capacitor side rather than the connection point of element 16a, 16b, 16c.

  The control unit 20 compares the load current input from the current detection unit 18 with a threshold value registered in advance, and if the load current is equal to or less than the threshold value, the first switching elements 16a, 16b, 16c and the second switching element 16 are compared. The switching elements 30 are turned off, and on / off control of these switching elements is not performed. As a result, the rectifier circuit shown in FIG. 4 has the circuit configuration shown in FIG.

  As described above, the level of the harmonic component included in the input current is within the IEC standard value even when the load is small and the DC voltage drop is small, particularly without the on / off control of the first switching elements 16a, 16b, and 16c. In the range below 1, the first switching elements 16a, 16b, 16c and the second switching element 30 are turned off, so that power loss due to switching can be reduced. Thereby, efficiency can be improved.

On the other hand, when the load current exceeds the threshold value, the second switching element 30 is turned on to connect the neutral point N of the three-phase AC power supply 11 and the connection point of the electrolytic capacitors 14a and 14b, and One switching element 16a, 16b, 16c is on / off controlled based on the voltage zero cross point and the load current.
As a result, when the load exceeds a predetermined level and the circuit configuration shown in FIG. 5 is unable to reduce the high frequency component to a specified value (for example, IEC standard value) or less, the above-described first By operating based on the same circuit configuration and control logic as the rectifier circuit according to the first embodiment, the DC voltage required for operation is maintained, and the high-frequency component included in the input current is set to be equal to or less than the IEC specified value. it can.

  As described above, according to the rectifier circuit according to the present embodiment, the load level is low, and even in a passive circuit configuration that does not use a switching element as in the circuit configuration illustrated in FIG. When the high frequency component to be generated can be equal to or lower than a predetermined specified value specified by IEC or the like, the first switching elements 16a, 16b, 16c and the second switching element 30 are turned off. Thereby, the power loss by switching can be suppressed and efficiency can be improved.

The load current threshold value for switching on / off of the second switching element 30 may be set based on the level and standard value of the high-frequency component included in the input current or based on the DC voltage required for operation.
In the first and second embodiments, the switching elements 16a, 16b, and 16c are connected to the connection line L1, and the neutral point N of the three-phase AC power source, the switching elements 16a, 16b, and 16c, and the connection point C are Are connected by the same connection line L1, but instead, the neutral point N and the connection point C of the three-phase AC power supply are connected to the switching elements 16a, 16b and 16c by separate connection lines. The point C may be connected.

1 is a circuit diagram showing a schematic configuration of a rectifier circuit according to a first embodiment of the present invention. It is the figure which showed the input voltage waveform input into a full wave rectifier circuit when the 1st and 2nd switching element with which the rectifier circuit which concerns on the 1st Embodiment of this invention is provided is made into an OFF state. It is the figure which showed the harmonic component contained in the input current at the time of applying the rectifier circuit which concerns on the 1st Embodiment of this invention. It is a circuit diagram which shows schematic structure of the rectifier circuit which concerns on the 2nd Embodiment of this invention. FIG. 5 is a diagram showing a circuit configuration when the first and second switching elements are turned off in the circuit diagram shown in FIG. 4. It is the figure which showed schematic structure of the rectifier circuit applied to the conventional single phase alternating current power supply. It is the figure which showed schematic structure of the rectifier circuit applied to the conventional three-phase alternating current power supply. It is the figure which showed the input voltage waveform input into a full wave rectifier circuit in the rectifier circuit shown in FIG. It is the figure which showed the input voltage waveform input into a full wave rectifier circuit in the rectifier circuit shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rectification circuit 11 Three-phase alternating current power supply 12a, 12b, 12c Reactor 13 Full wave rectification circuit 14a, 14b Electrolytic capacitor 15 Load 16a, 16b, 16c 1st switching element 17 Zero cross detection part 18 Current detection part 19 DC voltage detection part 20 Control Part 30 Second switching element L1 connection line

Claims (2)

A full-wave rectifier circuit connected via a reactor to the output side of each phase of the three-phase AC power supply;
A plurality of capacitors connected between output terminals of the full-wave rectifier circuit;
The plurality of capacitors are connected in series with each other,
A connection point of any one of the capacitors and a neutral point of the three-phase AC power supply are connected,
A rectifier circuit in which an input side of each phase of the full-wave rectifier circuit and a connection point of any one of the capacitors are connected via a first switching element. Any connection point of the capacitor and the neutral point of the three-phase AC power supply are connected via a second switching element,
When the load is equal to or less than a predetermined threshold value set in advance, the first switching element and the second switching element are turned off,
The rectifier circuit according to claim 1, wherein the second switching element is turned on when the load exceeds the threshold value.

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