JP2002369536A - Single-phase converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single-phase converter which can reduce harmonics components of an input current for the entire region of a load current. SOLUTION: This single-phase converter comprises a rectifier for full-wave rectification of single-phase alternate current, a DC reactor connected at one terminal to one terminal of output side of the rectifier, a switching element connected between the other terminal of the DC reactor and the other terminal on the output side of the rectifier, a reverse blocking diode connected to one terminal of the switching element, a smoothing capacitor connected between the output side of the reverse blocking diode and the other terminal of the switching element, a current detector for detecting an AC input current, and an active control means for controlling the switching element. Therefore, in this single-phase converter, the switching element starts to become conductive at the zero-cross point of the single-phase AC voltage, and the conductive state of the switching element is completed after the passage of time which depends on an amplitude of the AC input current detected with the current detector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-phase converter for converting AC input into DC power, and more particularly to a technique for reducing a harmonic component of an AC input current.

[0002]

2. Description of the Related Art Conventionally, an inverter for driving a compressor motor such as an air conditioner is operated by DC power converted from a single-phase AC power supply by a converter. FIG. 6 is a block diagram showing a configuration of a converter according to a conventional technique. In this figure, an AC power supply 1 is converted to a direct current by a rectifier 2 composed of diodes D1 to D4, smoothed by a DC reactor DCL and a capacitor C1, and supplied to a load 4. Usually, a large-capacity electrolytic capacitor is used as the capacitor.

[0003]

In the above-mentioned method, since the load viewed from the AC side is an inductance load, the phase of the flowing current becomes a lagging phase, and the current does not flow at the rising portion of the sine wave of the AC voltage. There has been a problem that a harmonic component included in the AC input current becomes large, and a large load may adversely affect the power supply system.
As a means for solving this problem, Japanese Patent Laid-Open No. 2-299470 discloses a technique in which a switching element is turned on at a rising portion of a sine wave of an AC voltage to forcibly flow a current and store energy in a reactor. ing.

However, the technique disclosed in Japanese Patent Application Laid-Open No. 2-299470 has a problem that since the time during which the switching element is turned on is fixed, it is not possible to reduce the harmonic component of the input current over the entire load current. there were.

The present invention has been made under such a background. By controlling the ON time of the switching element according to the magnitude of the load current, the harmonic component of the input current can be reduced over the entire load current. It is an object of the present invention to provide a single-phase converter capable of causing a single-phase converter.

[0006]

According to a first aspect of the present invention, there is provided a rectifier for performing full-wave rectification of a single-phase AC, a DC reactor having one end connected to one end on the output side of the rectifier, A switching element connected between the other end and the other end of the output side of the rectifier, a reverse blocking diode connected to one end of the switching element, an output side of the reverse blocking diode, and the other end of the switching element. And a current detector for detecting an AC input current, and active control means for controlling the switching element, wherein the active control means is provided at a zero crossing point of the single-phase AC voltage. The conduction of the switching element is started, and the conduction of the switching element is terminated after a lapse of time according to the magnitude of the AC input current detected by the current detector. Providing a single-phase converter, characterized in that.

According to the present invention, the input current waveform is improved by forcibly accumulating energy in the DC reactor by turning on the switching element at the rising portion of the AC voltage, thereby reducing the harmonic components of the input current. Can be.

According to a second aspect of the present invention, there is provided a rectifier for full-wave rectification of a single-phase alternating current, an AC reactor connected in series to an input side of the rectifier, and a switching element connected in parallel to an output side of the rectifier. A reverse blocking diode connected in series to one end on the output side of the rectifier; a smoothing capacitor connected between the output side of the reverse blocking diode and the other end on the output side of the rectifier; And an active control means for controlling the switching element, the active control means starting conduction of the switching element at a zero crossing point of the single-phase AC voltage, the current detector A switching device that terminates conduction of the switching element after a lapse of time according to the magnitude of the AC input current detected by the single-phase converter.

According to the present invention, an input current waveform is improved by forcibly storing energy in an AC reactor by turning on a switching element at a rising portion of an AC voltage to reduce a harmonic component of the input current. Can be.

[0010] Further, the invention according to claim 3 is based on claim 1.
3. The single-phase converter according to claim 2, wherein the conduction time of the switching element is such that when the AC input current increases, the conduction time is lengthened to reduce a harmonic component of the AC input current.

According to the present invention, the input current waveform can be improved regardless of the magnitude of the load, and the harmonic component of the input current can be reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a single-phase converter for converting AC input into DC power according to an embodiment of the present invention. In this figure, reference numeral 1 denotes an AC power supply, and diodes D1 to D4
Is connected to the AC input side of the rectifier 2 composed of.
A DC reactor DCL and a reverse blocking diode D5 connected in series are connected to a positive side of a DC output terminal of the rectifier 2, and a positive side of a smoothing capacitor C1 is connected to a cathode side of the diode D5. The connection point between the DC reactor DCL and the reverse blocking diode D5 is I
The collector of the switching element TR which is a GBT is connected, and the emitter of this switching element and the negative side of the smoothing capacitor C1 are connected to the negative side of the DC output terminal of the rectifier 2.

The load 4 is connected to both ends of the capacitor C1 and is supplied with required DC power. The load 4 is assumed to be an inverter that converts supplied DC power into three-phase AC and drives a motor, but may be any load. A current detector CT is provided on the AC input line, and switches the switching element TR via the active control means 3 based on the detected value.

Next, the switching of the switching element TR will be described with reference to FIGS. FIG. 2 is a diagram showing a relationship between an input power supply voltage, a switching element control pulse, and an input current waveform. The ON pulse of FIG. 2B is transmitted to the switching element TR by the pulse width T from the time t1 to the time t2 of the zero cross point of the input power supply voltage in FIG. The switching element TR is turned on by this ON pulse, the power supply voltage is applied to the DC reactor DCL, the input current increases as shown from the time t1 to the time t2 in FIG. 2C, and the energy by the flowing current is supplied to the DC reactor DCL. Stored. Switching element T at time t2
When R is turned off, the voltage polarity of the DC reactor DCL is inverted, and the current that has flowed immediately before is changed to the reverse blocking diode D.
Flow through 5. Further, as shown in FIG. 2C, the current continues to flow until time t3 as the power supply voltage increases. After time t3, the same operation as from time t1 described above is repeated.

FIG. 3 is a diagram showing the relationship between the AC input current value detected by the current detector CT and the pulse width for turning on the switching element TR generated by the active control means 3 in response to the current value. As shown in this figure, if the pulse width T is increased as the input current increases, the harmonic component of the input current can be reduced regardless of the magnitude of the input current.

FIG. 4 shows the IEC (Integer) shown for each harmonic order.
FIG. 3 is a diagram showing a regulation level of a rnational Electrotechnical Commission (International Electrotechnical Commission) and measured values according to the above-described embodiment. As can be seen from this figure, the present embodiment shows a result that is lower than the IEC regulation level up to higher-order harmonics.

Next, another embodiment of the present invention will be described with reference to FIG. This embodiment differs from the above-described embodiment in that an AC reactor ACL is provided in an AC input line instead of the DC reactor. The operation is the same as that of the above-described embodiment, but by arranging the reactor on the AC side, there is an advantage that consideration of DC bias is unnecessary and the design of the reactor is facilitated.

The operation of one embodiment of the present invention has been described above in detail with reference to the drawings. However, the present invention is not limited to this embodiment, and a design within a scope not departing from the gist of the present invention. Modifications and the like are included in the present invention. For example,
The type of load is not limited to the inverter, and may be any type of load. Further, the switching element is not limited to the IGBT, and may be another type of switching element.

[0019]

As described above, according to the first aspect of the present invention, the switching element is turned on at the rising portion of the AC voltage to forcibly accumulate energy in the DC reactor, thereby changing the input current waveform. This improves the effect of reducing harmonic components of the input current.

According to the second aspect of the present invention, the switching element is turned on at the rising portion of the AC voltage to forcibly accumulate energy in the AC reactor, thereby improving the input current waveform and reducing the harmonic components of the input current. The effect of being able to reduce is obtained. By arranging the reactor on the AC side, there is no need to consider DC bias.
There is an advantage that the design of the reactor becomes easy.

Further, according to the third aspect of the invention, it is possible to obtain an effect that the input current waveform can be improved irrespective of the magnitude of the load and the harmonic component of the input current can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a single-phase converter according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an input power supply voltage, a switching element control pulse, and an input current waveform.

FIG. 3 is a diagram showing a relationship between an input current and a switching element control pulse width.

FIG. 4 is a diagram showing an IEC regulation level for each harmonic order of an input current and an input harmonic current for each harmonic order generated according to an embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a single-phase converter according to another embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a single-phase converter according to a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... AC power supply 2 ... Rectifier 3 ... Active control means 4 ... Load CT ... Current detector C1 ... Capacitors D1-D5 ... Diode ACL ... AC reactor DCL ... DC reactor TR ... Switching element

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 3L060 AA01 CC10 DD08 EE04 5H006 AA01 AA02 CA01 CA07 CB01 CC08 DB01 DC02 DC04 5H740 BA11 BA18 BB05 NN03 NN08

Claims (3)

[Claims] 1. A rectifier for full-wave rectification of a single-phase alternating current, a DC reactor having one end connected to one end of an output side of the rectifier, and a second end between the other end of the DC reactor and the other end of the rectifier output side. A switching element connected to the switching element; a reverse blocking diode connected to one end of the switching element; a smoothing capacitor connected between the output side of the reverse blocking diode and the other end of the switching element; And an active control means for controlling the switching element, wherein the active control means starts conduction of the switching element at a zero crossing point of the single-phase AC voltage, and the current detector A single-phase converter that terminates conduction of the switching element after a lapse of time according to the magnitude of the AC input current detected by the switch. 2. A rectifier for full-wave rectification of single-phase AC, an AC reactor connected in series to an input side of the rectifier, a switching element connected in parallel to an output side of the rectifier, and an output side of the rectifier. A reverse blocking diode connected in series to one end, a smoothing capacitor connected between the output side of the reverse blocking diode and the other end on the output side of the rectifier, and a current detector for detecting an AC input current; An active control means for controlling the switching element, wherein the active control means starts conduction of the switching element at a zero crossing point of the single-phase AC voltage, and detects an AC input current detected by the current detector. A single-phase converter wherein the conduction of the switching element is terminated after a lapse of time according to the size. 3. The simple conduction time of the switching element according to claim 1, wherein the conduction time of the switching element increases as the AC input current increases to reduce a harmonic component of the AC input current. Phase converter.