JP2017169250A - Multilevel power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilevel power conversion device, in which switching loss is reduced thereby to achieve long life in a switching device as well as high efficiently, reduced size and low cost in the device.SOLUTION: A second switching device S2 is in "1" (ON-state) when voltages of [NP], [-E], and [-2E] are output. A seventh switching device S7 is in "1" (ON-state) when voltages of [+2E], [+E], and [NP] are output. Thus, switching in switching pattern transition of [+E]←→[NP] of the second switching device S2 and switching in switching pattern transition of [-E]←→[NP] of the seventh switching device S7 can be omitted.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a multilevel power conversion device, and more particularly to control of a switching pattern.

  FIG. 1 shows a single-phase multilevel power converter disclosed in [Embodiment 15] of Patent Document 1. The single-phase multilevel power conversion device shown in FIG. 1 includes first and second DC voltage sources DCP and DCN, first and second DC modules 1a and 1b, and a phase module 2.

  The first and second DC modules 1a and 1b have first and second flying capacitors FCP and FCN, and eight first to eighth semiconductor switches Sa to Sh.

  The phase module 2 includes ten first to eighth switching devices S1, S2, S3, S4a, S4b, S5a, S5b, S6, S7, and S8, and four first and second diodes D1a, D1b, and D2a. , D2b. In FIG. 1, IGBTs are shown as the first to eighth semiconductor switches Sa to Sh and the first to eighth switching devices S1 to S8, but other switches may be used.

  FIG. 3 shows a three-phase multilevel power conversion device in which the phase module 2 is provided for three phases.

  The voltages of the first and second DC voltage sources DCP and DCN are maintained at 2E [V], and the voltages of the first and second flying capacitors FCP and FCN of the first and second DC modules 1a and 1b are maintained at E [V]. By selecting the potentials of the DC modules 1a and 1b in the phase module 2, five potentials are output. Here, the current flowing through the output terminal O is I.

  Table 1 shows switching patterns of the first to eighth semiconductor switches Sa to Sh and the first to eighth switching devices S1 to S8 in the conventional five-level power converter.

  According to Table 1, the combination of these gate signals enables five potentials to be output. Here, the voltage output command of the phase module 2 is [+ 2E], [+ E], [NP], [−E], [−2E], and the voltage output command of the first and second DC modules 1a and 1b is [DD]. ], [CD], [DC], [CC]. The voltage output command [+ 2E] of the phase module 2 means that the voltage of the output terminal O with respect to the neutral point terminal N is + 2E. The same applies to [+ E], [−E], and [−2E]. The voltage output command [NP] of the phase module 2 means that the voltage of the output terminal O with respect to the neutral point terminal N is zero.

  Further, the output voltage of the phase module 2 is approximated to a sine wave. Therefore, the transition condition of the voltage output command of the phase module 2 is limited to [+ 2E] ← → [+ E] ← → [NP] ← → [−E] ← → [−2E].

  [D] of the voltage output command of the first and second DC modules 1a and 1b means a discharge command when the current I is positive, and [C] means a charge command. The first voltage output command of the first and second DC modules 1a and 1b is a command for the first flying capacitor FCP, and the second is a command for the second flying capacitor FCN.

  For example, in the case of the voltage output command [CD] of the first and second DC modules 1a and 1b, the first flying capacitor FCP means a charge command and the second flying capacitor FCN means a discharge command. In Table 1, 1 means gate on, and 0 means gate off. The first to eighth semiconductor switches Sa to Sh and the first to eighth switching devices S1 to S8 are turned on when the gate is turned on and turned off when the gate is turned off.

  FIG. 4 shows the operation of the multilevel power conversion device when the voltage output commands [+ 2E], [+ E], [NP], [−E], and [−2E] of the phase module 2 are used. The semiconductor switch, switching device, and diode surrounded by a circle are turned on, a current flows through the path shown in FIG. 4, and a voltage equal to the voltage output command is output to the output terminal O.

JP 2015-47056 A

  Although Patent Document 1 shows a five-level switching pattern, the number of times of switching is large when switching each level, and the switching loss increases.

  The locations enclosed in Table 1 are locations that require switching transitions (the switching pattern changes from 0 → 1 or 1 → 0). In particular, it can be seen that the second and seventh switching devices S2 and S7 have more switching times than the other switching devices. For this reason, the second and seventh switching devices S2 and S7 have a larger switching loss than other switching devices.

  As a result, there are problems such as shortening the life of the switching device and lowering the efficiency of the apparatus. Further, since the cooling mechanism of the apparatus needs to be increased due to the large switching loss, there has been a problem that the apparatus is increased in size and cost.

  As described above, in the multilevel power converter, there are problems in reducing switching loss, extending the life of the switching device, increasing the efficiency of the device, reducing the size, and reducing the cost.

  The present invention has been devised in view of the conventional problems, and one aspect thereof is connected to the first and second DC voltage sources connected in series and the first and second DC voltage sources. The first and second DC modules common to each phase, the first and second DC voltage sources, and the first and second DC modules are connected, and the first and second DC voltage sources and the first and first DC modules are connected to each other. A DC module having a switching device between each of the DC modules and the output terminal, and a phase module for each phase that selectively controls ON / OFF of the switching device, wherein the first DC module includes the first DC voltage source. A first semiconductor switch having one end connected to the positive electrode end, a fourth semiconductor switch having one end connected to the negative electrode end of the first DC voltage source, the other end of the first semiconductor switch, and the fourth semiconductor switch. Connected between the other end of the A flying capacitor, a second semiconductor switch having one end connected to a common connection point of the first semiconductor switch and the first flying capacitor, and one end connected to a common connection point of the first flying capacitor and the fourth semiconductor switch And a third semiconductor switch having the other end connected to the other end of the second semiconductor switch, and the second DC module has a first end connected to the positive end of the second DC voltage source. 5 semiconductor switches, an eighth semiconductor switch having one end connected to the negative electrode end of the second DC voltage source, and connected between the other end of the fifth semiconductor switch and the other end of the eighth semiconductor switch. A sixth semiconductor switch having one end connected to a common connection point of the second flying capacitor, the fifth semiconductor switch, and the second flying capacitor; A flying capacitor and a seventh semiconductor switch connected to a common connection point of the eighth semiconductor switch and the other end connected to the other end of the sixth semiconductor switch; and A first switching device having one end connected to a common connection point of the first semiconductor switch and the first flying capacitor; a second switching device having one end connected to a common connection point of the second and third semiconductor switches; A seventh switching device having one end connected to a common connection point of the sixth and seventh semiconductor switches; and an eighth switching device having one end connected to a common connection point of the second DC voltage source and the eighth semiconductor switch. Are connected in series between the common connection point of the first and second switching devices and the common connection point of the seventh and eighth switching devices. Are connected in series between the third, fourth, fifth and sixth switching devices, and the common connection point of the third and fourth switching devices and the common connection point of the fifth and sixth switching devices. First and second diodes, and a common connection point of the fourth and fifth semiconductor switches and a common connection point of the first and second diodes are connected to each other of the fourth and fifth switching devices. A multi-level power converter using a common connection point as an output terminal, characterized in that the semiconductor switch of the DC module and the switching device of the phase module are controlled by a switching pattern shown in Table 4 below.

In Table 4, 1 is gate-on and 0 is gate-off.

  As one aspect thereof, the phase module may be provided in three phases.

  ADVANTAGE OF THE INVENTION According to this invention, in a multilevel power converter device, it becomes possible to reduce a switching loss, to attain the lifetime improvement of a switching device, the high efficiency of an apparatus, size reduction, and cost reduction.

The circuit diagram which shows the multilevel power converter device in embodiment. The figure which shows operation | movement of the multilevel power converter device in embodiment. The circuit diagram which shows the multilevel power converter device which provided the phase module for three phases. The figure which shows operation | movement of the conventional multilevel power converter device.

  Hereinafter, an embodiment of a multilevel power conversion device according to the present invention will be described in detail with reference to FIGS.

[Embodiment]
The circuit configuration of the multilevel power conversion device of this embodiment is the same as that of FIG. 1 described in the related art. Hereinafter, the circuit configuration of the multilevel power conversion device according to the present embodiment will be described with reference to FIG.

  The multilevel power conversion device according to the present embodiment is provided for each phase, the first and second DC voltage sources DCP and DCN common to each phase, the first and second DC modules 1a and 1b common to each phase, and the respective phases. The phase module 2 selects a voltage and outputs it from the output terminal O.

  Hereinafter, a specific circuit configuration will be described. First and second DC voltage sources (DC capacitors or DC power supplies) DCP and DCN are connected in series, and a common connection point (neutral point) of the first and second DC voltage sources DCP and DCN is a neutral point terminal. N.

  The first and second DC modules 1a and 1b include first and fifth semiconductor switches Sa and Se having one ends connected to the positive ends of the first and second DC voltage sources DCP and DCN, and first and second DC modules. Fourth and eighth semiconductor switches Sd and Sh having one ends connected to the negative ends of the voltage sources DCP and DCN, the other ends of the first and fifth semiconductor switches Sa and Se, and the fourth and eighth semiconductor switches Sd and Sh. One end of the first and second flying capacitors FCP and FCN connected between the other ends of the first and second semiconductor switches Sa and Se and the first and second flying capacitors FCP and FCN. The connected second and sixth semiconductor switches Sb and Sf, one end connected to the common connection point of the first and second flying capacitors FCP and FCN and the fourth and eighth semiconductor switches, and the other end connected to the second and second semiconductor switches 6 semiconductor switch Sb, 3 connected to the other end of the f, and includes seventh semiconductor switch Sc, and Sg, the.

  The first and second DC modules 1a and 1b turn on the first and fifth semiconductor switches Sa and Se and the third and seventh semiconductor switches Sc and Sg, or turn on the fourth and eighth semiconductor switches Sd and Sh. 2. By turning on the sixth semiconductor switches Sb and Sf, voltages of E and −E levels are output to the phase module 2.

  The phase module 2 of each phase includes a common connection point of the first semiconductor switch Sa and the first DC voltage source DCP, a common connection point of the second and third semiconductor switches Sb and Sc, and a fourth and fifth semiconductor switch. The common connection point of Sd and Se, the common connection point of the sixth and seventh semiconductor switches Sf and Sg, and the common connection point of the eighth semiconductor switch Sd and the second DC voltage source DCN are connected as input terminals. .

  The phase module 2 connects one end of the first switching device S1 to a common connection point of the first semiconductor switch Sa and the first DC voltage source DCP, and a common connection point of the eighth semiconductor switch Sh and the second DC voltage source DCN. One end of the eighth switching device S8 is connected to One end of the second switching device S2 is connected to the common connection point of the second and third semiconductor switches Sb and Sc, and one end of the seventh switching device S7 is connected to the common connection point of the sixth and seventh semiconductor elements Sf and Sg. To do.

  The other ends of the first switching device S1 and the second switching device S2, the seventh switching device S7 and the eighth switching device S8 are connected to each other, and the common connection point of the first and second switching devices S1 and S2 is connected to the seventh and the seventh switching devices. The third to sixth switching devices S3 to S6 are sequentially connected in series between the common connection points of the eight switching devices S7 and S8.

  The first and second diodes D1a, D1b, D2a, and D2b are sequentially connected in series between the common connection point of the third and fourth switching devices S3 and S4a and the common connection point of the fifth and sixth switching devices S5b and S6. Connecting.

  A common connection point of the fourth and fifth semiconductor switches Sd and Se and a common connection point of the first and second diodes D1b and D2a are connected. A common connection point of the fourth and fifth switching devices S4b and S5b is defined as an output terminal O.

  Here, for the withstand voltage, the fourth switching devices S4a and S4b and the fifth switching devices S5a and S5b are connected in series, but if the withstand voltage problem is solved, the fourth and fifth switching devices S4b and S5b It can be omitted. Similarly, the first diodes D1a and D1b and the second diodes D2a and D2b are connected in series for withstanding voltage, but the first and second diodes D1b and D2b are omitted if the withstand voltage problem is solved. Is possible.

  In such a circuit configuration, the voltages of the first and second DC voltage sources DCP and DCN are controlled to 2E [V], and the voltages of the first and second flying capacitors FCP and FCN are controlled to E [V]. By selectively ON / OFF controlling the eighth semiconductor switches S1 to S8 and the first to eighth switching devices S1 to S8, any of the voltages of + 2E, + E, 0, −E, −2E A voltage can be output.

  Although the output voltage state of the multilevel power conversion device shown in FIG. 1 is five levels, the number of switching patterns is not limited to five. For example, when outputting + 2E and + E, the gate signal of the seventh switching device S7 can be output in either case of “1” or “0”.

  As described above, in the circuit configuration of FIG. 1, a plurality of switching patterns are not uniquely determined and exist. Therefore, the selection of the switching pattern can be freely designed according to the idea. The switching pattern design concept in the present embodiment is to minimize the number of times of switching and to reduce the switching loss.

  First, Table 2 shows a list of switching patterns that can output voltage.

  Since there are switching devices that do not affect the voltage output, in Table 2, switching devices that do not affect the output voltage are denoted by *. As shown in [0 output], [-E output], and [-2E output] in FIG. 4, the on / off state of the second switching device S2 is [0 output] and [-E output]. , [-2E output] is not related to the voltage output. Therefore, the columns [NP], [−E], and [−2E] of the second switching device S2 in Table 2 are “*”. The column of [+ 2E], [+ E], and [NP] that does not affect the voltage output for the seventh switching device S7 is marked with “*”.

  Next, Table 3 shows the case where the locations marked with “*” in Table 2 are selected so that the number of switching state transitions is minimized. Specifically, the fields [NP], [−E], [−2E] of the second switching device S2 are set to “1”, and [+ 2E], [+ E], [NP] of the seventh switching device S7 are set. The column is “1”.

  Compared to Table 1, Table 3 has fewer enclosed locations (locations where switching state transitions). Specifically, switching is performed when the switching pattern transition of [+ E] ← → [NP] of the second switching device S2 and when the switching pattern transition of [−E] ← → [NP] of the seventh switching device S7 is performed. I will not be broken.

  FIG. 2 shows the operation of the multilevel power conversion device when the voltage output commands [+ 2E], [+ E], [NP], [−E], and [−2E] in this embodiment shown in Table 3 are used. The semiconductor switch, switching device, and diode surrounded by a circle are turned on, a current flows through a path indicated by an arrow in FIG. 2, and a voltage equal to the voltage output command is output to the output terminal O.

  In addition, this embodiment is applicable to both the multilevel power converter of the converter circuit which converts AC power into DC power, and the multilevel power converter of the inverter circuit which converts DC power into AC power.

  Moreover, this embodiment is applicable also to the circuit which provided the phase module 2 for three phases as shown in FIG.

  As described above, according to the present embodiment, the number of switching times of the switching device of the multilevel power conversion device can be reduced, so that switching loss can be reduced. Thereby, the life of the switching device can be extended and the efficiency of the multilevel power conversion device can be increased. In addition, the cooling loss of the multilevel power converter can be reduced by reducing the switching loss, and the multilevel power converter can be reduced in size and cost.

  Although the present invention has been described in detail only for the specific examples described above, it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the technical idea of the present invention. Such variations and modifications are naturally within the scope of the claims.

DCP, DCN: first and second DC voltage sources FCP, FCN: first and second flying capacitors Sa to Sh: first to eighth semiconductor switches S1 to S8: first to eighth switching devices D1a, D1b, D2a , D2b ... 1st, 2nd diode 1a, 1b ... 1st, 2nd DC module 2 ... Phase module

Claims (2)

First and second DC voltage sources connected in series, first and second DC modules common to each phase connected to the first and second DC voltage sources, and the first and second DC voltage sources, The switching device is connected to the first and second DC modules, and has a switching device between the first and second DC voltage sources, the first and second DC modules, and an output terminal, and the switching device is selectively turned on. , And a phase module for each phase to be controlled OFF,
The first DC module includes:
A first semiconductor switch having one end connected to the positive terminal of the first DC voltage source;
A fourth semiconductor switch having one end connected to the negative end of the first DC voltage source;
A first flying capacitor connected between the other end of the first semiconductor switch and the other end of the fourth semiconductor switch;
A second semiconductor switch having one end connected to a common connection point of the first semiconductor switch and the first flying capacitor;
A third semiconductor switch having one end connected to a common connection point of the first flying capacitor and the fourth semiconductor switch and the other end connected to the other end of the second semiconductor switch; the second DC module Is
A fifth semiconductor switch having one end connected to the positive terminal of the second DC voltage source;
An eighth semiconductor switch having one end connected to the negative end of the second DC voltage source;
A second flying capacitor connected between the other end of the fifth semiconductor switch and the other end of the eighth semiconductor switch;
A sixth semiconductor switch having one end connected to a common connection point of the fifth semiconductor switch and the second flying capacitor;
A seventh semiconductor switch having one end connected to a common connection point of the second flying capacitor and the eighth semiconductor switch and the other end connected to the other end of the sixth semiconductor switch;
The phase module is in each phase,
A first switching device having one end connected to a common connection point of the first semiconductor switch and the first flying capacitor;
A second switching device having one end connected to a common connection point of the second and third semiconductor switches;
A seventh switching device having one end connected to a common connection point of the sixth and seventh semiconductor switches;
An eighth switching device having one end connected to a common connection point of the second DC voltage source and the eighth semiconductor switch;
Third, fourth, fifth, and sixth switching devices sequentially connected in series between the common connection point of the first and second switching devices and the common connection point of the seventh and eighth switching devices;
First and second diodes sequentially connected in series between a common connection point of the third and fourth switching devices and a common connection point of the fifth and sixth switching devices;
Have
A multi-level power converter that connects a common connection point of the fourth and fifth semiconductor switches and a common connection point of the first and second diodes and uses a common connection point of the fourth and fifth switching devices as an output terminal. Because
The multi-level power converter characterized by controlling the semiconductor switch of the said DC module and the switching device of a phase module by the switching pattern of the following Table 4.

In Table 4, 1 is gate-on and 0 is gate-off.   The multi-level power converter according to claim 1, wherein the phase module is provided in three phases.

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