JP3478701B2 - Three-phase power factor improving converter - Google Patents

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching type DC stabilized power supply device intended to suppress harmonic currents in a three-phase three-wire AC power supply.

[0002] (2)

2. Description of the Related Art In three-phase three-wire AC power supply, a method is known in which three converters having a single-phase harmonic suppression function are connected between each phase and their outputs are connected in parallel to form a power supply circuit. Has been.

[0003]

However, in the conventional configuration, since each converter has a separate control circuit, the harmonic component of each phase current is reduced, but the balance of each phase current, that is, each converter is The loads to be shared do not necessarily become the same, and a slight difference in the output voltage setting of each control circuit causes a large difference in each phase current.
Therefore, it has been difficult to realize a power supply circuit with the conventional configuration without the load balancing function.

Therefore, an object of the present invention is to realize a three-phase power factor improving converter having a circuit configuration similar to that of the prior art and a simple method, in which phase currents are balanced.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of this circuit. In the three-phase three-wire AC power supply, first, the boost chopper circuit 1 is connected between the U phase and the V phase. The boost chopper circuit 1 includes a full wave rectifier 2, an inductor 3, a switch element 4, a rectifying element 5,
The control circuit 7 is configured so that the U-phase current composed of the capacitor 6 is proportional to the voltage waveform between the U-phase and the N-phase, and that the output voltage V1 is a constant DC voltage.

Next, a DC-DC converter 8 which receives the output V1 of the boost chopper circuit 1 as an input is connected.
The DC-DC converter 8 is a forward converter including switch elements 9 and 10, a transformer 11, rectifying elements (3) 12 and 13, an inductor 14, and a capacitor 15, and a control circuit 16 that outputs a DC voltage output V0. Switch elements 9 and 1
The on / off timing of 0 is controlled. still,
The forward converter is a method of supplying power to the output when the switching element is turned on, and a half-bridge or full-bridge converter is also included in this range.

The circuit configurations of the step-up chopper circuit 1 connected between the U-phase and the V-phase, the step-up chopper circuit 17 connected in the V-phase-W correlation, and the step-up chopper circuit 18 connected between the W-phase and the U-phase are as follows. Assuming the same, each output voltage V
The respective control circuits are set so that 1, V2, V3 are V1 = V2 = V3 under constant input / output conditions.

Furthermore, each output voltage has a regulation characteristic that the voltage drops as the load increases. Further, DC-DC converters 8, 19 and 20 are connected to the outputs of the boost chopper circuits, respectively. These DC-D
The C converters have the same circuit configuration, and their outputs are connected in parallel and supplied to the load 21. The DC voltage V0 supplied to the load 21 is kept constant by the control circuit 16.
In addition, the control circuit 16 causes each DC-DC converter 8, 1
The drive signals sent to the switch elements 9 and 10 of 9 and 20 are the same.

In such a circuit configuration, if the DC-DC converters 8, 19 and 20 have the same input voltage and the same output voltage as described above, and the drive signals of the main switches are also the same, DC-DC converters 8, 19,
The load shared by 20 is also the same. That is, each DC-
The electric power converted by the step-up chopper circuits 1, 17, 18 supplying the input voltage to the DC converters 8, 19, 20 is also the same, and if there is no voltage imbalance in the three-phase three-wire (4) type AC power supply, The phase currents of the U, V and W phases are also the same.

Even if the load of the step-up chopper circuit for a certain phase increases more than that of the other step-up chopper circuit, its output voltage has the regulation characteristic that the voltage drops as the load increases. As the input voltage of the converter decreases, the load currents shared by the DC-DC converters 8, 19, 20 work in a balanced direction.

By the method as described above, it becomes possible to simultaneously satisfy harmonic suppression and current balance of each phase current, which cannot be achieved by the conventional structure.

[0012]

According to the present invention, in the three-phase three-wire AC power supply, the suppression of the harmonic component of the phase current and the balance of each phase current are simultaneously satisfied with a very simple circuit configuration.

[Brief description of drawings]

FIG. 1 is a harmonic suppression power supply circuit for 3-phase 4-wire AC power supply.

[Simple explanation of symbols]

1,17,18 Boost chopper circuit 2 full wave rectifier 3,14 inductor 4,9,10 switch element 5,12,13 Rectifier 6,15 capacitors 7,16 Control circuit 8, 19, 20 DC-DC converter 11 transformers 21 load

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Claims (4)

(57) [Claims] 1. A circuit configuration in which three sets of single-phase converters having a harmonic suppression function are connected between each phase of a three-phase three-wire type AC power supply, wherein a single-phase input power supply between the phases is provided with a boost chopper circuit, An insulation type DC-DC converter having this output as an input is respectively connected, each output of the insulation type DC-DC converter is connected in parallel, and the main switch of the DC-DC converter is driven by the same control signal. A three-phase power factor improvement type converter characterized in that 2. The three-phase power factor improving converter according to claim 1, wherein the output voltages of the boost chopper circuits have the same value. 3. The three-phase power factor improving converter according to claim 2, wherein the currents of the isolated DC-DC converters are balanced by the regulation of the output voltage of each of the boost chopper circuits. A characteristic three-phase power factor improvement type converter. 4. The three-phase power factor improving type converter according to claim 1, wherein each of the insulation type DC-DC converters is a forward type DC-DC converter. converter.