JPH03265467A - Three-phase converter circuit - Google Patents

Abstract

PURPOSE:To reduce the size, the weight and the cost by connecting AC reactors, respectively, between two AC input terminals and the neutral terminals of upper and lower arms provided with three pairs of arms and switching elements. CONSTITUTION:One terminal of AC reactors 1, 2 are connected with AC input terminals U, V whereas the other terminals thereof are connected with the neutral terminals of two pairs of arms comprising switching elements 4, 5, 6, 7. The remaining AC input terminal W is connected with the neutral terminal of a pair of arms comprising only diodes 14, 15. Three pairs of arms are connected into a three-phase bridge and an electrolytic capacitor 16 is connected between DC output terminals P, N. Switching elements in two pairs of arms are ON/OFF controlled according to the interval relevant to the relation of magnitudes of AC input voltage between respective phases thus bringing the power factor of input current approximately to 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a three-phase converter circuit, and more specifically, the average magnitude of the input current from a three-phase AC power source is a sine wave with a power factor of approximately 1. The present invention relates to a three-phase high power factor converter circuit that operates as shown in FIG.

(Prior Art) FIG. 4 shows a conventional three-phase converter circuit of this type.

In the figure, one terminal of AC reactors 1 to 3 is connected to three-phase AC input terminals U, V, and W, respectively.

The other terminal is connected to transistors 4, 5.6, 7°8.
9, respectively, are connected to the midpoint terminals of three pairs of upper and lower arms. Further, these three pairs of upper and lower arms are connected in a three-phase bridge, and an electrolytic capacitor 16 is connected between the DC output terminals P and N.

Further, transistors 4 to 9 are connected to diodes 10 to 1, respectively.
5 are connected in parallel in opposite directions.

In such a circuit configuration, by controlling the on/off of transistors 4 to 9 by a control circuit (not shown), the average magnitude of the input current from the three-phase AC input terminals U, V, and W can be adjusted. It operates to form a sine wave with a power factor of approximately 1, and a smoothed DC voltage is output from DC output terminals P and N.

(Problems to be Solved by the Invention) The conventional circuit described above requires six transistors as switching elements of the converter, six diodes as rectifying elements, and three AC reactors, so the number of components is large. It has been difficult to make the device smaller, lighter, and cheaper.

The present invention has been made to solve the above problems,
The purpose is to provide a three-phase converter circuit that can simplify the circuit configuration, reduce the size, weight, and cost of the device by reducing the number of parts.

(Means for Solving the Problem) In order to achieve the above object, the present invention provides a switch element such as a transistor in one of the three upper and lower arm pairs connected in a three-phase bridge in a conventional circuit configuration. By removing the The number of switch elements and AC reactors is reduced.

That is, the present invention provides a three-phase converter circuit that outputs a DC voltage higher than a voltage obtained by full-wave rectifying a three-phase AC voltage by a three-phase bridge rectifier circuit, in which one of the three upper and lower arm pairs constituting the three-phase bridge rectifier circuit. Each of the two upper and lower arm pairs includes a switch element, and first and second AC reactors are connected between the midpoint terminals of these two upper and lower arm pairs and the two AC input terminals, and the other One pair of upper and lower arms is configured with only rectifying elements, the midpoint terminal of this pair of upper and lower arms is directly connected to one other AC input terminal, and a capacitor or other storage battery is connected between the DC output terminals of the three-phase bridge rectifier circuit. It is a connection of means.

(Function) According to the present invention, by controlling the on/off of the switch elements of the two upper and lower arm pairs according to the period focusing on the magnitude relationship of each phase AC input voltage, the switch required in the conventional circuit is Even when six elements are reduced to four, and three AC reactors are reduced to two, the device can be operated so that the average magnitude of the input current becomes a sine wave with a power factor of approximately 1.

This makes it possible to make the three-phase high power factor converter circuit smaller, lighter, and cheaper.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, and the same components as in FIG. 4 are given the same reference numerals. That is, in the circuit configuration, one terminal of the AC reactor 1.2 is two AC input terminals U.

(2), and the other terminal is connected to the midpoint terminal of the pair of upper and lower arms, each consisting of transistors 4, 5, 6, and 7 as switching elements. Furthermore, diodes 10 to 13 are connected in antiparallel to these transistors 4 to 7, respectively.

On the other hand, the remaining AC input terminal W is connected to the diode 14.
It is directly connected to the midpoint terminal of the upper and lower arm pair consisting of only 15. Three pairs of upper and lower arms, each consisting of transistors 4 to 7 and diodes 10 to 15, are connected in a three-phase bridge, and an electrolytic capacitor 16 is connected between their DC output terminals P and N.

In such a circuit configuration, by selecting the inductance e1t i+2 of the AC reactor 1.2 to the same value, the principle of operation is explained below so that the average magnitude of the input current becomes a sine wave with a power factor of 1. explain.

Figure 2 shows the three-phase AC voltage waveform input to the AC input terminals U, V, and W. In Figure 2, one cycle of the three-phase AC voltage is divided into 12 periods from A to L. . In addition, in these periods A-L, the relationship among the U-phase voltage Vu, V-phase voltage Vv, and W-phase voltage Vw, which are three-phase AC voltages, is as follows.

Period A: Vu>Vw>Vv, Vw>OB: Vu>
Vw>Vv, Vv<OC: Vu>Vv>Vw, Vv<OD: Vu>Vv>Vw, Vv>O E: Vv>Vu>Vw, Vu>0 F: Vv>Vu>Vww Vu< OG : V
v) Vw>Vu, Vw<OH: Vv>Vv>Vu, Vw> O I: Vw>Vv>Vu, Vv> OJ: V
w>Vv>Vu, Vv<OK: Vw>Vu>Vv,
Vu<O L: Vw>Vu>Vv, Vu> 0 First, in period A, as mentioned above, the relationship between Vu, Vv, and Vv is Vu
>Vv)Vv, and since Vw>0(V) (neutral point voltage), Vv>(Vu+Vv). During this period, if the transistor 6 in the upper arm of the V phase is turned on in the embodiment shown in FIG.
Current flows through the phase path, and then from the U phase to AC reactor 1
- Diode 10 - Transistor 6 - AC reactor 2
A current flows through the path, and energy is accumulated in each of the AC reactors 1 and 2.

At this time, the currents Iu and Iv of the U phase, ■ phase, and W phase.

The rate of change of Iv, ΔIu, ΔIv, ΔIw, is determined by AC reactor 1 (inductance a) and AC reactor 2 (inductance a)
) is C1=a, and V v ) (V
u+Vv), the potential of the DC output terminal P is clamped to the W-phase potential, and the result is as follows.

ΔI u = (Vu - Vw) / a□ΔI v=
(Vv −Vw)/l12ΔIw=−(ΔIu+ΔI
v) = (Vu Vw+Vv Vv)/at= 3
(Vw)/111 Next, if this transistor 6 is turned off, the energy stored in the AC reactors 1 and 2 is transferred from the W phase to the diode 14 - electrolytic capacitor 16 - diode 1.
The electrolytic capacitor 16 is charged because it is discharged through the path of 3-AC reactor 2-V phase and the path of AC reactor 1-diode 10-electrolytic capacitor 16-diode 13-AC reactor 2-V phase from U phase. and these AC reactors 1 and 2 are reset. By repeating turning on and off of the transistor 6 at regular intervals in this manner, this converter circuit can be operated as a step-up converter.

Here, if this step-up ratio is set sufficiently large, the reset time of AC reactors 1 and 2 will be sufficiently small compared to the on period of transistor 6, and as a result, the current flowing in the U phase, ■ phase, and W phase 1 u.

The average size of Iv and Iw is determined by the current change rate Δ
It is proportional to the magnitude of Iu, ΔIv, and ΔIw.

Therefore, by adjusting the on/off period of the transistor 6, it is possible to control the average magnitude of the W-phase current Iw.

Furthermore, if the average magnitude of Iw is controlled to a value such that the power factor of the three-phase AC input is approximately l, then Iu
The average magnitude of is also smaller than the value for making the power factor approximately 1. Therefore, by newly turning on transistor 5 during the period when transistor 6 is turned off, current flows from the U phase through the path of AC reactor 1 - transistor 5 - diode 13 - AC reactor 2 - V phase, and the W phase current It becomes possible to increase the U-phase current Iu regardless of 1w.

From the above, in period A shown in FIG. 2, by adjusting on/off of transistors 5 and 6,
It becomes possible to control the average magnitude of the U-phase and W-phase currents Iu and Iw in a region where the power factor of the three-phase AC input is approximately 1.

Further, period B in FIG. 2 can be similarly controlled by adjusting transistors 5 and 6, and period G and H can also be similarly controlled by adjusting transistors 4 and 7.

Next, in period C, by turning on transistor 5, current flows from the U phase to AC reactor 1 - transistor 5 - diode 15 - W phase, energy is stored in AC reactor 1, and transistor 5 is turned off. Then, the energy of the AC reactor 1 is charged to the electrolytic capacitor 16 through the path of AC reactor 1 - diode 10 - electrolytic capacitor 16 - diode 15 - W phase from the U phase, and the AC reactor 1 is reset to perform a boost operation. By adjusting the on/off of this transistor 5,
It becomes possible to control the average magnitude of the W-phase current Iw.

Furthermore, by turning on the transistor 6 while the transistor 5 is off, the current flows from the U phase to the AC reactor 1 - diode 10 - transistor 6 - AC reactor 2 - phase ■, regardless of the W phase current 1. By passing a current, energy is accumulated in the AC reactors 1 and 2, and when the transistor 6 is turned off, the energy is transferred from the U phase to the AC reactor 1 - diode 10 -
The electrolytic capacitor 16 is charged through the path of electrolytic capacitor 16 - diode 13 - AC reactor 2 - V phase.

By adjusting on/off of this transistor 6, V
It becomes possible to control the phase current 1v.

From the above, in period C, by adjusting on/off of transistors 5 and 6.

It becomes possible to control the average magnitude of the W-phase and V-phase currents Iw and Iv in a region where the power factor of the three-phase AC input is approximately 1. Also 1 period F, I.

Control can be performed in the same manner for the case of L.

Next, during a period, by turning on transistors 5 and 7, the U phase is connected to AC reactor 1 - transistor 5.
- Flow current through the diode 15-W phase path and the AC reactor 2-transistor 7-diode 15-W phase path from the ■phase to store energy in each AC reactor 1 and 2, and turn off the transistor 5. in,
The energy stored in AC reactor 1 is transferred from U phase to AC reactor 1 - diode 1 - electrolytic capacitor 16
- Diode 15 - By charging the electrolytic capacitor 16 through the W phase path and performing a step-up operation, and similarly turning off the transistor 7, the energy stored in the AC reactor 2 is transferred from the V phase to the AC reactor 2 - diode 12 - The electrolytic capacitor 16 is charged through the path of electrolytic capacitor 16 - diode 15 - W phase, and boost operation is performed. Here, by adjusting on/off of transistors 5 and 7, the current Iu of U phase and V phase is increased. , Iv can be controlled in a region where the power factor of the three-phase AC input is approximately 1. Further, it is possible to control the periods E and J in the same way.

From the above, in the embodiment shown in FIG. 1, by adjusting on/off of transistors 4 to 7, the average magnitude of the input current from the three-phase AC input can be adjusted to approximately 1 power factor.
This makes it possible to create a sine wave.

Next, FIG. 3 shows a second embodiment of the present invention.

In this embodiment, one terminal of the AC reactors 1, 2 is connected to the AC input terminals U, 2, respectively, and the other terminal is connected to the switching elements 17, 18, 19, 2, such as transistors.
0, respectively, are connected to the midpoint terminals of the two upper and lower arm pairs. Furthermore, the remaining AC input terminal W is connected to diode 1.
4.15 is directly connected to the midpoint terminal of the upper and lower arm pair. These three pairs of upper and lower arms are connected in a three-phase bridge, and an electrolytic capacitor 16 is connected between the DC output terminals P and N.

In such a circuit configuration, the inductance Q1. of the AC reactor 1.2. By choosing the same value for a,
The principle of operation so that the average magnitude of the input current becomes a sine wave with a power factor of approximately 1 is the same as that of the first embodiment, and is the same as the on/off adjustment of transistors 4 to 7 in FIG. The adjustment is performed by turning on and off the switching elements 17 to 20, respectively.6 Furthermore, the diodes 10 to 1 in FIG.
3, the switch element 17 is configured to function in the same way as the diode in the operation mode in which current flows through any one of the diodes.
By adjusting the on/off state of any one of the elements 20 to 20, the same operation as in FIG. 1 can be achieved.

With the above adjustment, it is possible to make the average magnitude of the input current from the three-phase AC input terminal a sine wave with a power factor of approximately 1, as in the first embodiment.

(Effects of the Invention) As described above, according to the present invention, the three-phase AC power supply operates so that the average magnitude of the input current becomes a sine wave with a power factor of approximately 1, and outputs a DC voltage. In the phase high power factor converter circuit, the number of switching elements required has been reduced from 6 to 4 compared to conventional circuits, and the number of AC reactors has been reduced to 3.
It can be reduced from one to two. As a result, it is possible to simplify the circuit configuration, reduce the size and weight of the device, and reduce the cost.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, and FIG. 2 is an AC input voltage waveform diagram for explaining the operation of the first embodiment.
FIG. 3 is a circuit diagram showing a second embodiment of the present invention, and FIG. 4 is a circuit diagram showing a conventional technique. 1-3... AC reactor 4-9... Transistor 10-15... Diode 16... Electrolytic capacitor 17-20... Switch element

Claims (1)

[Claims] In a three-phase converter circuit that outputs a DC voltage higher than a voltage obtained by full-wave rectifying a three-phase AC voltage using a three-phase bridge rectifier circuit, the three-phase bridge rectifier circuit includes three pairs of upper and lower arms constituting the three-phase bridge rectifier circuit. Two of the upper and lower arm pairs each include a switch element, and first and second AC reactors are connected between the midpoint terminals of these two upper and lower arm pairs and the two AC input terminals, and the other One pair of upper and lower arms is constructed of only rectifying elements, the midpoint terminal of this pair of upper and lower arms is directly connected to the other AC input terminal, and a power storage means is connected between the DC output terminals of the three-phase bridge rectifier circuit. A three-phase converter circuit characterized in that: