JPH0993944A - 3-phase high power factor converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the distortion factors and the negative-phase-sequence current factors of AC input currents of the respective phases of a 3-phase high power factor converter. SOLUTION: A plurality of switching devices 6a, 6b, 6c and 6d or switching devices 6a and 6b are connected in series between the DC terminals of a 3-phase full-wave rectifier 3 which is composed of diodes 3a-3f in a 3-phase high power factor converter. In the former case, the series connection points other than the middle connection point are connected to DC output terminals and, in the latter case, the switching devices 6c and 6d are connected between the DC terminals of the 3-phase full-wave rectifier 3 and the DC output terminals. Further, capacitors 2a-2c, diodes 7a and 7b and choking coils 4a-4c are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-phase high power factor converter, and more specifically, it can shape an AC input current of each phase into a sine wave having the same phase as the AC input voltage of each phase. The present invention relates to a three-phase high power factor converter capable of reducing the distortion factor and the equivalent anti-phase current factor.

[0002]

2. Description of the Related Art A conventional three-phase high power factor converter is available from
There is one described in FIG. 8 of a paper entitled "Analysis of New Single-Phase Input Current Sinusoidal Rectifier Circuit" in a material issued by the Institute of Electrical Engineers, Semiconductor Power Conversion Study Group on October 29, 1993.

The conventional three-phase high power factor converter described above is as shown in FIG.

That is, the three-phase high power factor converter shown in FIG. 5 performs full-wave rectification of the three-phase AC power from the three-phase AC power supply 1 with the diodes 3a, 3b, 3c, 3d, 3e,
A three-phase full-wave rectifier circuit 3 composed of 3f, and a choke coil 4a inserted between each AC terminal of the three-phase full-wave rectifier circuit 3 and each phase terminal R, S, T of the three-phase AC power supply 1. , 4
b, 4c, a series connection circuit of two switching elements 6a, 6b connected between the DC terminals of the three-phase full-wave rectification circuit 3, and an output capacitor 5, and each phase terminal R of the three-phase AC power supply 1. , S, T, one end of each of which is connected to the intermediate series connection point N of the switching elements 6a, 6b, and the other end of which is commonly connected to the capacitors 2a, 2b,
2c and diodes 7a and 7b connected in antiparallel to the switching elements 6a and 6b, respectively, and the terminal of the output capacitor 5 is connected to the DC output terminals t1 and t2 to which the load R _L is connected. At the same time, the switching elements 6a and 6b are turned on and off at a frequency higher than the frequency of the three-phase AC power source 1 by a control circuit (not shown) so that the AC input current of each phase is in the same phase as the AC input voltage of each phase. It is shaped like a wave.

Next, the operation of the conventional three-phase high power factor converter described above will be described based on the operation mode diagram of the switching elements 6a and 6b in FIG.

(Mode 1) When the switching element 6a is on and the switching element 6b is off, the phase voltage of each phase of the three-phase AC power supply, that is, the intermediate series connection point of the R phase switching elements 6a and 6b. If the potential of N, that is, the common connection point (neutral point) of the capacitors 2a, 2b, and 2c is positive, the potential of the S-phase neutral point is negative, and the potential of the T-phase neutral point is negative, the capacitors 2a and 3 Connection point with phase AC power supply 1 → choke coil 4a → diode 3a
→ Switching element 6a → Current flows in the path of neutral point. The current in this path is a current for accumulating energy in the choke coil 4a and is therefore proportional to the phase voltage of the R phase.

(Mode 2) When the switching element 6a is off and the switching element 6b is off, R
When the phase voltages of the S, S, and T phases are the same as in mode 1, the path is choke coil 4a → diode 3a → output capacitor 5 → diode 7b → capacitor 2a → choke coil 4a, and choke coil 4a → diode 3a → output capacitor. 5 → diode 3d (diode 3f) →
An electric current flows through a path () which is a connection point between the choke coil 4b (choke coil 4c) and the capacitor 2b and the three-phase AC power supply 1 (a connection point between the capacitor 2c and the three-phase AC power supply 1). The currents in this path and the path () are due to the release of the energy accumulated in the choke coil 4a, and therefore are not proportional to the phase voltages of the R phase, S phase, and T phase.

(Mode 3) When the switching element 6a is off and the switching element 6b is on, R
When the phase voltage of the S-phase, S-phase, and T-phase is the same as in mode 1, the neutral point → switching element 6b → diode 3d (diode 3f) → choke coil 4b (choke coil 4c) →
A path () that is a connection point between the capacitor 2b and the three-phase AC power supply 1 (connection point between the capacitor 2c and the three-phase AC power supply 1)
Current flows through. The current in this path, which is a current for storing energy in the choke coils 4b and 4c, is proportional to the phase voltage of the S phase and T phase.

(Mode 4) When the switching element 6a is off and the switching element 6b is off, R
When the phase voltage of the S-phase, S-phase, and T-phase is the same as in mode 1, choke coil 4b (choke coil 4c) → diode 3c
(Diode 3e) → Output capacitor 5 → Diode 7
An electric current flows through a path () which is formed of b → capacitor 2b (capacitor 2c) → choke coil 4b (choke coil 4c). The current in this path () is the choke coil 4
It is not proportional to the phase voltage of the S phase and T phase because it is due to the release of energy accumulated in b and 4c.

The above description of each mode is the same even when the polarities of the phase voltages of the respective phases of the three-phase AC power supply 1 are different, and therefore the description thereof is omitted.

In each of the above modes, the switching elements 6a and 6b are turned on and off by a control circuit (not shown), which is higher than the frequency of the three-phase AC power source 1 by several tens of k.
It is done in Hz.

Regarding the conventional three-phase high power factor converter described above, the three-phase AC input voltage is 180V, 200V, 220.
V, 240V, 264V, DC output voltage 390
When a harmonic analysis of the AC input current of the R phase was performed with V and DC output power of 6479 W, the results shown in Table 1 were obtained.

[0013]

[Table 1]

From Table 1, it can be seen that among the harmonic components of the R-phase AC input current, the fifth harmonic component and the seventh harmonic component are large, and as a result, the distortion factor and the equivalent anti-phase current factor are large. I understand. The same applies to the S and T phases other than the R phase.

This means that the switching elements 6a and 6b are
When is on, a current proportional to the phase voltage of each phase, that is, a current for storing energy flows in the choke coils 4a, 4b, 4c, but the switching elements 6a, 6b.
When is off, a current that is not proportional to the phase voltage of each phase, that is, a current for discharging the energy accumulated in the choke coils 4a, 4b, and 4c flows.

[0016]

As described above, the conventional three-phase high power factor converter has a problem that the distortion factor of the AC input current and the equivalent anti-phase current factor are large.

[0017]

In order to solve the above problems, the present invention provides a three-phase full-wave rectifier circuit for full-wave rectifying the three-phase AC power from a three-phase AC power supply, and the three-phase full-wave rectifier circuit. A choke coil inserted between each AC terminal and each phase terminal of the three-phase AC power supply, a series connection circuit of a plurality of switching elements connected between the DC terminals of the three-phase full-wave rectifier circuit, A capacitor having one end connected to each phase terminal of the three-phase AC power supply and the other end commonly connected to the intermediate series connection point of the switching elements, and the plurality of switching elements having a frequency of the three-phase AC power supply. In a three-phase high power factor converter having a control circuit for turning on and off at a higher frequency, a plurality of switching elements is composed of a series connection circuit of four switching elements and is connected at an intermediate series connection point. A diode is connected in antiparallel to each of the two switching elements, two series connection points other than the intermediate series connection point are connected to a DC output terminal, and an output capacitor is connected between the DC output terminals. To do.

Further, in the three-phase high power factor converter according to the present invention, the plurality of switching elements comprises a series connection circuit of two switching elements, and each switching element has a DC terminal of a three-phase full-wave rectification circuit. A switching element between each DC output terminal and each DC output terminal, and a diode connected between each DC output terminal and the intermediate series connection point of the switching elements, and an output capacitor between the DC output terminals. It is characterized by connecting.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
~ It demonstrates based on FIG.

1 and 3 are circuit diagrams of a three-phase high power factor converter according to an embodiment of the present invention. Portions having the same functions as those in FIG. 5 are designated by the same reference numerals, and the following description will be omitted. .

FIG. 2 is an operation waveform diagram of each switching element of the three-phase high power factor converter of FIG. 1, and FIG. 4 is an operation mode diagram of each switching element of the three-phase high power factor converter of FIG. The following description of the same operation as 6 will be omitted.

The characteristic of the three-phase high power factor converter shown in FIG. 1 is that, of the two switching elements 6a, 6b whose one ends are connected to each other at the intermediate series connection point N, the switching element is provided at the other end of the switching element 6a. 6c is connected to one end, the other end of the switching element 6b is connected to one end of the switching element 6d, and the other ends of the switching elements 6c and 6d are connected to the DC terminal of the three-phase full-wave rectification circuit 3. is there.

Then, the switching elements 6a to 6d
Operate as in the operation mode diagram shown in FIG.

(Mode 1) Switching element 6a is on, switching element 6b is off, switching element 6
When c is on and the switching element 6d is on, this is the same as the operation in mode 1 of the conventional three-phase high power factor converter described above.

(Mode 2) Switching element 6a is off, switching element 6b is off, switching element 6
When c is on and the switching element 6d is off, the current of the path in the mode 2 of the conventional three-phase high power factor converter described above is prevented from flowing and only the current of the path is not proportional to the phase voltage. .

(Mode 3) Switching element 6a is off, switching element 6b is on, switching element 6
When c is on and switching 6d is on, the operation is the same as the operation in mode 3 of the conventional three-phase high power factor converter described above.

(Mode 4) Switching element 6a is off, switching element 6b is off, switching element 6
When c is off and the switching element 6d is on, the current in the path in the mode 4 of the conventional three-phase high power factor converter described above is prevented from flowing and the current not proportional to the phase voltage is eliminated.

In the above description of each mode, it is only in mode 2 that a current not proportional to the phase voltage does not flow, but in mode 2 depending on the polarity of the phase voltage of each phase of the three-phase AC power supply 1,
In both mode 4, a current that is not proportional to the phase voltage flows,
It goes without saying that a current that is not proportional to the phase voltage flows only in mode 4.

Next, the feature of the three-phase high power factor converter shown in FIG. 3 is that one ends are connected to each other at an intermediate series connection point N,
Of the two switching elements 6a, 6b whose other end is connected to the DC terminal of the three-phase full-wave rectifier circuit 3, the connection point of the switching element 6a with the DC terminal of the three-phase full-wave rectifier circuit 3 and the DC output. The switching element 6c is inserted between the terminal t1 and the switching element 6d between the connection point of the switching element 6b with the DC terminal of the three-phase full-wave rectifier circuit 3 and the DC output terminal t2, and the DC output The diode 7a is connected between the terminal t1 and the intermediate series connection point N, and the diode 7b is connected between the DC output terminal t2 and the intermediate series connection point N.

Then, the switching elements 6a to 6d
Operate as in the operation mode diagram shown in FIG.

(Mode 1) Switching element 6a is on, switching element 6b is off, switching element 6
When c is on and the switching element 6d is on, this is the same as the operation in mode 1 of the conventional three-phase high power factor converter described above.

(Mode 2) Switching element 6a is off, switching element 6b is off, switching element 6
When c is on and the switching element 6d is off, the current of the path in the mode 2 of the conventional three-phase high power factor converter described above is prevented from flowing and only the current of the path is not proportional to the phase voltage. .

(Mode 3) Switching element 6a is off, switching element 6b is on, switching element 6
When c is on and the switching element 6d is on, this is the same as the operation in mode 3 of the conventional three-phase high power factor converter described above.

(Mode 4) Switching element 6a is off, switching element 6b is off, switching element 6
When c is off and the switching element 6d is on, the current of the path in the mode 4 of the conventional three-phase high power factor converter described above is prevented from flowing and the current not proportional to the phase voltage is eliminated.

In the above description of each mode, only the mode 2 does not flow a current that is not proportional to the phase voltage, but the mode 2, depending on the polarity of the phase voltage of each phase of the three-phase AC power supply 1.
In both mode 4, a current that is not proportional to the phase voltage flows,
It goes without saying that a current that is not proportional to the phase voltage flows only in mode 4.

Of the three-phase high power factor converter of the present invention described above, the three-phase AC input voltage of the one shown in FIG.
When V, 200V, 220V, 240V, and 264V were set, the DC output voltage was 390V, and the DC output power was 6479W, the harmonic analysis of the R phase AC input current was performed, and the results shown in Table 2 were obtained.

[0037]

[Table 2]

It can be seen from Table 2 that the fifth harmonic component and the seventh harmonic component of the harmonic component of the AC input current of the R phase could be suppressed, and thereby the distortion factor and the equivalent reverse phase were obtained. It can be seen that the current rate could be reduced. The same applies to the S and T phases other than the R phase.

The difference between the one shown in FIG. 1 and the one shown in FIG. 3 is that in FIG. 1, the current in the path in mode 1 flows through the switching elements 6c and 6a, and the current in the path in mode 3 switches. 3 flows in the elements 6b and 6d, the current in the path in mode 1 flows in the switching element 6a and the current in the path in mode 3 flows in the switching element 6b. The loss due to the switching element can be reduced.

It should be noted that the switching elements 6c and 6d in both FIG. 1 and FIG. 3 described above are turned on and off in the state where no current is flowing, so that zero current switching is performed and the switching elements 6c and 6d are turned on. There is no increase in switching loss due to insertion.

[0041]

As has been described above, the three-phase high power factor converter of the present invention allows the AC input current of each of the three phases to be supplied to each phase without increasing the loss due to the addition of the switching element. It can be shaped into a sine wave having the same phase as the AC input voltage, and its distortion factor and equivalent anti-phase current ratio can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a three-phase high power factor converter according to an embodiment of the present invention.

2 is an operation mode diagram of a switching element in the embodiment of FIG.

FIG. 3 is a circuit diagram of a three-phase high power factor converter according to another embodiment of the present invention.

4 is an operation mode diagram of a switching element in the embodiment of FIG.

FIG. 5 is a circuit diagram of a conventional three-phase high power factor converter.

FIG. 6 is an operation mode diagram of a switching element in a conventional three-phase high power factor converter.

[Explanation of symbols]

 1 Three-phase AC power supply 2a, 2b, 2c Capacitor 3 Three-phase full-wave rectifier circuit 4a, 4b, 4c Choke coil 5 Output capacitor 6a, 6b, 6c, 6d Switching element 7a, 7b Diode

Claims (2)

[Claims] 1. A three-phase full-wave rectification circuit for full-wave rectifying three-phase AC power from a three-phase AC power supply, and an AC terminal of the three-phase full-wave rectification circuit and each phase terminal of the three-phase AC power supply. A choke coil inserted between them, a series connection circuit of a plurality of switching elements connected between the DC terminals of the three-phase full-wave rectifier circuit, and one end of each of the phase terminals of the three-phase AC power supply are connected. A three-phase having a capacitor whose other end is commonly connected to an intermediate series connection point of the switching elements, and a control circuit for turning on / off the plurality of switching elements at a frequency higher than the frequency of the three-phase AC power supply In a high power factor converter, a plurality of switching elements are composed of a series connection circuit of four switching elements, and two switching elements connected at an intermediate series connection point are connected in antiparallel to each other. A three-phase high power factor converter characterized by connecting a battery, connecting two series connection points other than the intermediate series connection point to a DC output terminal, and connecting an output capacitor between the DC output terminals. 2. The three-phase high power factor converter according to claim 1, wherein the plurality of switching elements comprises a series connection circuit of two switching elements, and
Insert a switching element between each DC output terminal and the connection point with the DC terminal of the three-phase full-wave rectifier circuit, and connect a diode between each DC output terminal and the intermediate series connection point of the switching element. And a three-phase high power factor converter characterized in that an output capacitor is connected between the DC output terminals.