TWI678870B - Power conversion device and power conversion system - Google Patents

Abstract

A power conversion device according to an embodiment of the present invention includes a first power conversion circuit that converts and outputs power from an external input, and a second power conversion circuit that is connected to the first power conversion circuit via a DC link unit, and The input power is converted and output to the load; a smoothing capacitor is provided at the output portion of the first power conversion circuit and an input portion of the second power conversion circuit; a first common mode extraction circuit is provided at the input of the first power conversion circuit The second common mode extraction circuit, which is provided at the output of the second power conversion circuit; the imaginary neutral potential line, which connects the first common mode extraction circuit and the second common mode extraction circuit; the DC link filter circuit, which A Y-type capacitor connected between the DC link section and the imaginary neutral potential line; the first common mode coil is inserted at the connection point of the Y-type capacitor from the first common mode extraction circuit to the DC link filter circuit A path; and a second common-mode coil inserted in a path from the connection point of the Y-type capacitor to the second common-mode extraction circuit.

Description

Power conversion device and power conversion system

Embodiments of the present invention relate to a device and system for converting electric power input from the outside and outputting the electric power to a load.

For example, if the metal components of a power conversion device such as an inverter and a load device such as a motor are arranged to face the ground potential, a parasitic capacitance is formed between the two, and a leakage occurs through the parasitic capacitance. Current. Since the leakage current will cause deterioration of the mechanical device and unexpected electric shock, it must be as close as possible to 0A. In addition, due to the high performance of the semiconductor switching device, the high-frequency operation of the power conversion device becomes high. Since the impedance of the parasitic capacitance decreases with the increase in frequency, measures against leakage current become more important.

To suppress leakage current, for example, the impedance against the common mode is increased. Specifically, measures such as increasing the distance between the ground potential and the opposing metal, or inserting a high-inductance common-mode choke coil into a power line, etc. However, any of these countermeasures has a problem that leads to an increase in the size of the power conversion device. In addition to countermeasures against leakage current, in order to suppress electromagnetic noise, a capacitor may be intentionally connected to a ground potential. In this case, if a capacitor with a large capacitance is selected in order to make the noise suppression effect effective at a low frequency, an increase in leakage current will be caused.

Provided are a power conversion device and a power conversion system having a function capable of avoiding an increase in size and suppressing a leakage current.

The power conversion device of the embodiment includes: The first power conversion circuit converts and outputs power input from the outside; the second power conversion circuit connects to the first power conversion circuit via a DC link section, and converts the input power and outputs it to a load. A smoothing capacitor provided in the output portion of the first power conversion circuit and an input portion of the second power conversion circuit; a first common mode extraction circuit provided in the input portion of the first power conversion circuit; the second total A mode extraction circuit is provided in the output section of the second power conversion circuit; an imaginary neutral potential line connects the first common mode extraction circuit and the second common mode extraction circuit; a DC link filter circuit having a connection A Y-type capacitor between the aforementioned DC link portion and the aforementioned imaginary neutral potential line; a first common mode coil which is inserted from the aforementioned first common mode extraction circuit to the aforementioned Y-type capacitor of the aforementioned DC link filter circuit Point; and a second common-mode coil inserted from the connection point of the Y-type capacitor to the path of the second common-mode extraction circuit.

In addition, the so-called "Y-type capacitor" here means that one end of two capacitors is connected in common, and one end of the aforementioned common is connected to a virtual neutral potential line, and the other end of each of the two capacitors is connected to a DC link. A line that connects the first and second power conversion circuits in the road section.

1‧‧‧Power Conversion Device

2‧‧‧ converter

3‧‧‧Three-phase AC power / power supply

4‧‧‧External impedance adjustment circuit

4u‧‧‧coil

4v‧‧‧coil

4w‧‧‧coil

5‧‧‧The first common mode extraction circuit

5u‧‧‧capacitor

5v‧‧‧Capacitor

5w‧‧‧capacitor

6‧‧‧imaginary neutral potential line

7‧‧‧DC Link Department

8‧‧‧ Inverter

9‧‧‧DC link filter circuit / filter circuit

10‧‧‧ Common mode choke coil / coil

11‧‧‧Common mode choke coil / coil

12‧‧‧Y-type capacitor / Y-capacitor

12a‧‧‧Capacitor

12b‧‧‧Capacitor

13‧‧‧Smoothing capacitor

14‧‧‧ smoothing capacitor

15‧‧‧Three-phase motor / motor

15u‧‧‧Stator coil

15v‧‧‧ Stator coil

15w‧‧‧stator coil

16‧‧‧The second common mode extraction circuit

16A‧‧‧Common mode choke coil

16B‧‧‧Common mode choke coil

16C‧‧‧Common mode choke coil

16u‧‧‧capacitor

16v‧‧‧Capacitor

16w‧‧‧capacitor

17‧‧‧LC filter circuit

18‧‧‧ capacitor

19‧‧‧ Coil

20‧‧‧Capacitor

21‧‧‧DC link filter circuit

22‧‧‧ Coil

23‧‧‧Power Conversion Device

31‧‧‧Power Conversion Device

32‧‧‧ Power

33‧‧‧DC-DC converter

34‧‧‧External impedance adjustment circuit

35‧‧‧The first common mode extraction circuit

36‧‧‧DC-AC Inverter / Inverter

37‧‧‧External impedance adjustment circuit

38‧‧‧Load

39‧‧‧The second common mode extraction circuit

41‧‧‧Power Conversion Device

42‧‧‧Load

43‧‧‧External impedance adjustment circuit

43a‧‧‧Common mode choke coil

43b‧‧‧Capacitor

44‧‧‧ converter

45‧‧‧Current limit circuit

46‧‧‧DC link filter circuit / filter circuit

47‧‧‧Smoothing capacitor

48‧‧‧imaginary neutral potential common line

49‧‧‧Current limit circuit

E‧‧‧ Earth

FIG. 1 is a first embodiment showing a functional block diagram of a power conversion device composed of a three-phase AC input / three-phase AC output.

FIG. 2 is a diagram showing a configuration of a DC link filter circuit in part according to a second embodiment.

FIG. 3 is a view showing the structure of the first embodiment in more detail, showing a third embodiment.

FIG. 4 is a diagram showing a waveform of a leakage current generated when the configuration of the third embodiment is applied.

FIG. 5 is a diagram showing a waveform of a leakage current generated when a previous configuration is applied.

Fig. 6 is a fourth embodiment showing a functional block diagram of a power conversion device applied to a power conditioner.

Fig. 7 is a fifth embodiment showing a functional block diagram of a power conversion device in which a second power conversion circuit is connected in parallel.

FIG. 8 is a sixth embodiment, and is a functional block diagram briefly showing the configuration of the power conversion device.

FIG. 9 is a seventh embodiment, and is a functional block diagram briefly showing the configuration of the power conversion device.

Fig. 10 is an eighth embodiment, and is a functional block diagram briefly showing the configuration of the power conversion device.

Therefore, there is provided a power conversion device and a power conversion system having a function capable of preventing an increase in size and suppressing a leakage current.

The power conversion device according to the embodiment includes: a first power conversion circuit that converts and outputs power from an external source; and a second power conversion circuit that is connected to the first power conversion circuit through a DC link unit, and The input power is converted and output to the load; the smoothing capacitor is provided in the output section of the first power conversion circuit and the input section of the second power conversion circuit; the first common mode extraction circuit is provided in the first power conversion An input portion of the circuit; a second common-mode extraction circuit provided at the output portion of the second power conversion circuit; An imaginary neutral potential line connecting the first common mode extraction circuit and the second common mode extraction circuit; a DC link filter circuit having a Y connected between the DC link portion and the imaginary neutral potential line Type capacitor; a first common-mode coil inserted from the aforementioned first common-mode extraction circuit to a connection point of the aforementioned Y-type capacitor of the DC link filter circuit; and a second common-mode coil inserted from the aforementioned Y-type capacitor The path from the connection point of the capacitor to the aforementioned second common mode extraction circuit.

In addition, the so-called "Y-type capacitor" here means that one end of two capacitors is connected in common, and one end of the aforementioned common is connected to a virtual neutral potential line, and the other end of each of the two capacitors is connected to a DC link. A line that connects the first and second power conversion circuits in the road section.

(First Embodiment)

Hereinafter, the first embodiment will be described with reference to FIG. 1. Figure 1 shows a three-phase AC input / three-phase AC output power conversion device. The power conversion device 1 includes a converter 2 which is disposed on the input side and corresponds to a first power conversion circuit. The three-phase input terminals of the converter 2 are respectively connected to the respective phase terminals of the three-phase AC power source 3 through the external impedance adjustment circuit 4. The external impedance adjustment circuit 4 includes coils 4u, 4v, and 4w corresponding to each of them.

A first common-mode extraction circuit 5 is connected to the three-phase input terminal of the converter 2. The first common mode extraction circuit 5 includes, for example, capacitors corresponding to each not shown. One end of the three capacitors is connected to a corresponding phase, and the other end is commonly connected to a virtual neutral potential line 6. The first common-mode extraction circuit 5 extracts a common-mode current flowing in the three-phase AC power line and flows it to the virtual neutral potential line 6. The first common mode extraction circuit 5 may include a common mode choke coil connected in series between the three-phase capacitor and the virtual neutral potential line 6. Converter 2 will be converted by the input three-phase AC power Change to DC power and output.

The output terminal of the converter 2 is connected to the input terminal of the inverter 8 corresponding to the second power conversion circuit on the output side via the DC link section 7. A DC link filter circuit 9 is inserted into the DC link section 7. The filter circuit 9 includes a series circuit of common mode choke coils 10 and 11. One end of the coil 10 is connected to the output terminal of the converter 2, and one end of the coil 11 is connected to the input terminal of the inverter 8. That is, the series circuits of the coils 10 and 11 are inserted in the path from the converter 2 to the inverter 8. The coils 10 and 11 correspond to the first and second common mode choke coils, respectively.

One terminal of the two capacitors 12a and 12b is connected to the common connection point of the coils 10 and 11, respectively, and the other ends of the capacitors 12a and 12b are connected to the virtual neutral potential line 6 in common. Hereinafter, the two capacitors 12 a and 12 b connected to the other end in common may be referred to as a Y-type capacitor 12. The filter circuit 9 is a so-called T-type common mode filter. Further, smoothing capacitors 13 and 14 are connected between the output terminals of the converter 2 and the input terminals of the inverter 8.

Each phase output terminal of the inverter 8 is connected to a load, that is, a stator coil of each phase of the three-phase motor 15. A second common mode extraction circuit 16 similar to the first common mode extraction circuit 5 is connected between the output terminals of the respective phases and the virtual neutral potential line 6. The casing of the motor 15 and the power source 3 are grounded to the ground E, respectively. An LC filter circuit 17 is connected between the virtual neutral potential line 6 and the ground E. The LC filter circuit 17 includes a capacitor 18 connected between the virtual neutral potential line 6 and the ground E, and a series circuit of a coil 19 and a capacitor 20 connected in parallel to the capacitor 18.

According to this embodiment configured as described above, compared with the previous configuration of Patent Document 1, the DC link section 7 is provided with the DC link filter circuit 9, and is provided between the DC link filter circuit 9 and the ground E. The LC filter circuit 17 can further increase the effect of suppressing leakage current. In addition, by providing the external impedance adjustment circuit 4, the impedance on the side of the virtual neutral potential line 6 is relatively reduced, and the effect of suppressing leakage current can be further improved.

(Second Embodiment)

In the following, the same parts as those in the first embodiment are given the same reference numerals and descriptions thereof are omitted, and different parts will be described. FIG. 2 partially shows the constitution of the DC link filter circuit 21 in place of the second embodiment of the DC link filter circuit 9. The DC link filter circuit 21 has a coil 22 inserted between a common connection point of the Y capacitor 12 and the virtual neutral potential line 6. By using the DC link filter circuit 21 as described above, the selectivity of the frequency for suppressing the leakage current can be improved.

(Third Embodiment)

The power conversion device 23 according to the third embodiment shown in FIG. 3 is a configuration in which each component of the power conversion device 1 according to the first embodiment is shown in more detail, and a part of it is changed. The first common mode extraction circuit 5 includes capacitors 5u, 5v, and 5w corresponding to each of them as described in the first embodiment. The second common mode extraction circuit 16 includes corresponding capacitors 16u, 16v, and 16w, and common mode choke coils 16A, 16B, and 16C connected between them and the virtual neutral potential line 6.

The converter 2 and the inverter 8 are configured by three-phase bridging of six switching elements. Recirculation diodes are connected in antiparallel to each switching element, and capacitors are connected in parallel between respective phase bridge arms. In addition, the motor 15 displays parasitic capacitances formed between the wiring resistance or the wiring inductance and the ground E in addition to the stator coils 15u, 15v, and 15w of each phase. As a variation of the LC filter circuit 17, the direction connected between the virtual neutral potential line 6 and the ground E is set to be opposite to the first embodiment.

The time constant of the LC filter circuit 17 is used to suppress the component that generates a peak leakage current at a frequency higher than the switching frequency of the converter 2 and the inverter 8 by the resonance phenomenon, and has a low impedance at the frequency at which the aforementioned peak is generated. Way to set. At this time, the total capacitance of the LC filter circuit 17 is set to such an extent that the leakage current component at the switching frequency does not become a problem.

Respectively, FIG. 5 shows a leakage current waveform generated with respect to the previous configuration of Patent Document 1, and FIG. 4 shows a leakage current waveform generated with respect to the configuration of the third embodiment. We carry out in 3rd In the configuration of the form, the maximum amplitude of the leakage current is about 1/4 of the previous configuration.

(Fourth Embodiment)

The power conversion device 31 of the fourth embodiment shown in FIG. 6 is used for a power conditioner used in, for example, a solar power generation device. The power source 32 is, for example, a solar cell, and generates and outputs DC power. A DC-DC converter 33 corresponding to the first power conversion circuit is connected to the power source 32 via an external impedance adjustment circuit 34. The external impedance adjustment circuit 34 is composed of, for example, a common mode choke coil. A first common mode extraction circuit 35 is connected between the input terminal of the DC-DC converter 33 and the virtual neutral potential line 6. The DC-DC converter 33 converts the input DC voltage into a different voltage and outputs it.

The output terminal of the DC-DC converter 33 is connected to the input terminal of the DC-AC inverter 36 corresponding to the second power conversion circuit via the DC link section 7. An output terminal of the inverter 36 is connected to a load 38 via an external impedance adjustment circuit 37. The inverter 36 converts the input DC power into single-phase AC power and outputs it to the load 38. The load 38 is a single-phase AC power line such as a commercial AC power system. A second common mode extraction circuit 39 is connected between the output terminal of the inverter 36 and the virtual neutral potential line 6. In addition, the first and second common mode extraction circuits 35 and 39 may be connected only when the impedance adjustment is necessary according to the leakage current or the occurrence of noise.

According to the fourth embodiment configured as described above, the power conversion device 31 can be applied to a power conditioner.

(Fifth Embodiment)

The power conversion device 41 of the fifth embodiment shown in FIG. 7 has a configuration in which two second power conversion circuits are connected in parallel to the DC link section 7. The converter 44 connected between the DC link section 7 and the load 42 via the external impedance adjustment circuit 43 performs DC-DC conversion. The external impedance adjustment circuit 43 includes a common-mode choke coil 43 a and a capacitor 43 b connected between terminals on the load 42 side. in A second common mode extraction circuit 39 is connected between the output terminal of the converter 44 and the virtual neutral potential line 6. A current limiting circuit 45 is inserted into the virtual neutral potential line 6. The current limiting circuit 45 is configured to prevent an excessive current from flowing in the imaginary neutral potential line 6. For example, the current limiting circuit 45 may be composed of a resistor unit or an inductor unit, and may be a circuit including a RC parallel circuit in consideration of frequency characteristics.

A smoothing capacitor 47, an inverter 8 and a three-phase motor 15 are connected to the output terminal of the converter 2 via another DC link filter circuit 46. The filter circuit 46 corresponds to a parallel DC link filter circuit. Each phase output terminal of the inverter 8 is connected to an input terminal of the second common mode extraction circuit 16. The common connection point of the Y-type capacitor constituting the DC link filter circuit 46 is connected to the virtual neutral potential line 6 via the virtual neutral potential common line 48. Another current limiting circuit 49 is connected between the second common mode extraction circuit 16 and the imaginary neutral potential common line 48.

In addition, the connection form of the imaginary neutral potential common line 48 is not limited to those shown in the figure, but may be connected to a portion other than the power line. When the leakage current becomes large at a plurality of frequencies, the time constant is designed such that the LC filter circuit 17 has a low impedance at the frequency.

According to the fifth embodiment configured as described above, the converter 44 and the inverter 8 as the second power conversion circuit are connected in parallel to the DC link section 7 and the virtual neutral potential line 6 is shared. In a configuration in which each of them is operated, leakage current can be suppressed.

(6th to 8th embodiments)

The sixth to eighth embodiments show changes in the positions where the first and second common mode choke coils are inserted. In addition, in FIG. 8 to FIG. 10 corresponding to these embodiments, the symbols corresponding to the structures of the first embodiment are briefly shown, and the Y-type capacitor 12 of the DC link section 9 is also represented by a capacitor. .

In the sixth embodiment shown in FIG. 8, the common mode choke coil 11 is inserted from the inverter 8 to the first 2 The path of the common mode extraction circuit 16.

In the seventh embodiment shown in FIG. 9, the common mode choke coil 10 is inserted into the path from the first common mode extraction circuit 5 to the converter 2.

In the eighth embodiment shown in FIG. 10, the common mode choke coil 10 is inserted in the path from the first common mode extraction circuit 5 to the converter 2, and the common mode choke coil 11 is inserted in the inverter 8 to Path of the second common mode extraction circuit 16. The same effects as those of the first embodiment can be obtained in the case of such a configuration.

(Other embodiments)

The first power conversion circuit may be configured to perform power conversion using diode rectification.

In the first to fourth and sixth to eighth embodiments, the current limiting circuit can be inserted into the virtual neutral potential line 6.

When two or more power conversion devices according to the first to fourth and sixth to eighth embodiments are used in parallel, the power conversion system can be constructed by connecting the imaginary neutral potential lines 6 in common.

In the fifth embodiment, the second and subsequent power conversion circuits can be configured in parallel to three or more groups.

Although several embodiments of the present invention have been described, these embodiments are proposed as examples, and are not intended to limit the scope of the present invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and variations are included in the scope and gist of the present invention, and are included in the inventions and their equivalents described in the scope of patent application.

Claims (15)

A power conversion device having the following configuration: a first power conversion circuit that converts and outputs power from an external input; and a second power conversion circuit that is connected to the first power conversion circuit through a DC link section, and The input power is converted and output to a load; a smoothing capacitor is provided in the output section of the first power conversion circuit and an input section of the second power conversion circuit; a first common mode extraction circuit is provided in the first section An input section of the power conversion circuit; a second common mode extraction circuit provided in the output section of the second power conversion circuit; an imaginary neutral potential line connecting the first common mode extraction circuit and the second common mode extraction circuit A DC link filter circuit having a Y-type capacitor connected between the DC link portion and the imaginary neutral potential line; a first common mode coil inserted between the first common mode extraction circuit and the DC A path of the connection point of the aforementioned Y-type capacitor of the link filter circuit; and a second common mode coil inserted from the connection point of the aforementioned Y-type capacitor to the aforementioned second common mode extraction circuit Path. For example, the power conversion device of claim 1, wherein the first and second common mode coils are connected in series and arranged in the DC link filter circuit; the Y-type capacitor is connected to the first and second common mode coils. Between the common connection point and the aforementioned imaginary neutral potential line. The power conversion device according to claim 1 or 2, wherein the filter circuit includes a coil inserted between a common connection point of the Y-type capacitor and the imaginary neutral potential line. The power conversion device according to claim 1 includes an LC filter circuit connected between the aforementioned virtual neutral potential line and the ground potential. The power conversion device according to claim 2, further comprising an LC filter circuit connected between the aforementioned virtual neutral potential line and the ground potential. The power conversion device according to claim 3, further comprising an LC filter circuit connected between the imaginary neutral potential line and the ground potential. The power conversion device according to claim 1, wherein the input section of the first common mode extraction circuit and / or the output section of the second common mode extraction circuit includes an external impedance adjustment circuit. The power conversion device according to claim 2, wherein the input portion of the first common mode extraction circuit and / or the output portion of the second common mode extraction circuit includes an external impedance adjustment circuit. The power conversion device according to claim 3, wherein the input section of the first common mode extraction circuit and / or the output section of the second common mode extraction circuit includes an external impedance adjustment circuit. The power conversion device according to claim 4, wherein the input portion of the first common mode extraction circuit and / or the output portion of the second common mode extraction circuit includes an external impedance adjustment circuit. The power conversion device according to claim 5, wherein the input section of the first common mode extraction circuit and / or the output section of the second common mode extraction circuit includes an external impedance adjustment circuit. The power conversion device according to claim 6, wherein the input section of the first common mode extraction circuit and / or the output section of the second common mode extraction circuit includes an external impedance adjustment circuit. For example, the power conversion device of claim 1 includes: two or more parallel power conversion circuits corresponding to the second power conversion circuit; and a parallel DC link section that connects the output section of the first power conversion circuit and the parallel power. Between the input portions of the conversion circuit; and a parallel DC link filter circuit connected between the parallel DC link portion and the imaginary neutral potential line. The power conversion device according to claim 1, further comprising a current limiting circuit inserted in the aforementioned virtual neutral potential line. A power conversion system includes the following configuration: a plurality of power conversion devices such as the item 1 of claim 1; and a virtual neutral potential line of the plurality of power conversion devices is connected in common.