JP2013078204A - Power converting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power converter that has a series constitution of semiconductor elements as a main constitution and can deal with a high voltage and multiple output levels without using a transformer.SOLUTION: In order to deal with a high voltage, a leg 1 of a voltage-type converter is constituted of series connections of a plurality of semiconductor elements 101 through 112. Taking economic efficiency into account, the semiconductor elements having the same rating are used. Further, since a DC circuit 2 is also subjected to the high voltage, the DC circuit 2 is constituted of series connections of DC capacitors 201 through 206. In such constitutions, connection points among pairs adjacent to one another of the semiconductor elements 101 through 112 constituting the leg 1 and connection points among pairs adjacent to one another of the individual DC capacitors 201 through 206 are connected by switches 41 through 44 constituted of semiconductor elements having the same voltage ratings as those of the semiconductor elements 101 through 112 constituting the leg 1. An output voltage of the number of voltage levels corresponding to the number of capacitors 201 through 206 connected in series in the DC circuit 2 is generated at an output terminal U.

Description

  The present invention relates to a power conversion device applied to a motor drive inverter, a frequency conversion device, or the like that converts high voltage power.

  As a conventional technique, a conversion device using a diode clamp circuit and a conversion device using a neutral point switch as a conversion device that outputs a three-level voltage are disclosed in papers and the like. The basic configuration of these circuits is shown in FIGS.

  First, the operation of the prior art will be described with reference to FIG.

  FIG. 13 shows the configuration of one phase of the power converter. For single-phase output, this configuration is used in one set (half-bridge single-phase output circuit) or two sets (full-bridge single-phase output circuit). Three sets are used for phase output. U is an AC output of the power converter, and three levels of voltages, DC voltages + E, 0, and −E, maintained by the DC circuit 2 are output by turning on and off the semiconductors 101 to 104 in the leg 1. The width of the voltage step is adjusted by PWM control, and an AC voltage having a desired frequency and voltage is applied to the load.

  When outputting + E voltage to the U phase, the semiconductor elements 101 and 102 are turned on. In order to output 0 voltage, the semiconductor elements 102 and 103 are turned on. In this state, the DC neutral point C and the AC output terminal U are connected through the diode clamp circuit 3. When outputting the voltage −E, the semiconductor elements 103 and 104 are turned on. In this way, three levels of voltage are output.

  Next, another conventional technique will be described with reference to FIG.

  FIG. 14 shows the configuration for one phase of the power converter. For single-phase output, this configuration is similarly set to one set (half-bridge single-phase output circuit) or two sets (full-bridge single-phase output circuit). Use three sets for three-phase output. The operation is almost the same as the example of FIG. 13 except that the DC neutral point C and the AC output terminal U are connected by turning on the neutral point switch 6 to output 0 voltage. . In the configuration of FIG. 13 showing the prior art, the neutral point switch is configured by connecting in parallel a circuit in which the diodes 301 and 302 and the transistors 102 and 103 are connected in series, but the diode and the transistor are reversed as shown in FIG. Even if the configurations 6A and 6B connected in parallel are connected in series, the same function is realized. In a general IGBT element, a transistor and a diode are connected in antiparallel, so that it is practical to configure a switch using the transistor. Therefore, FIG. 14 shows an example in which a switch is configured by connecting IGBTs in series in opposite directions.

  As a semiconductor element used in these technologies, a self-excited (self-extinguishing) IGBT element or the like is practically used, and an economically available semiconductor element has a voltage rating of about 1000 V. Many of these techniques are applied to power converters having an output of about several hundred volts.

“A New Neutral-Point-Clamped PWM Inverter”, Akira Nabae et al., IEEE Transaction on Industry Applications, Vol. IA-17, No.5 September / October 1981 pp.518-523

In order to save energy and reduce CO _2, a technology for driving a pump or a fan motor at a variable speed with an inverter is widely used. However, most of these inverters have a rated voltage of about several hundred volts for the reasons described above. High voltage motors used in large-scale plants and the like have a plurality of low voltage inverters connected via transformers. Inverter connected in series. However, in such a configuration, since a transformer is required, there are problems such as an increase in weight and size and a large restriction on an installation location.

  In order to solve the above-described problem, the embodiment provides a power converter capable of handling high voltages and multiple output levels without using a transformer, with a series configuration of semiconductor elements as a central configuration.

  An example of means for solving the above problems is as follows.

  In order to handle a high voltage, the legs of the voltage source converter are configured by connecting a plurality of semiconductor elements in series. Considering economic efficiency, use semiconductor elements with the same rating. Further, since the DC circuit also has a high voltage, it is configured by connecting DC capacitors in series. In this configuration, the connection point between the semiconductor elements constituting the leg and the connection point between the DC capacitors are connected by a switch composed of a semiconductor element having the same rating as the semiconductor element constituting the leg. . The output voltage of the number of levels corresponding to the number of capacitors connected in series in the DC circuit is generated.

    That is, in the power conversion device according to the embodiment, a circuit element composed of an anti-parallel connection of a diode and a switching element is configured as a semiconductor element, and a plurality of 2n capacitors (n is a natural number) having the same voltage rating are connected in series. A circuit and a series circuit in which 4n semiconductor elements having the same voltage rating are connected in series, the leg being connected in parallel with the DC circuit by a positive and negative bus, and the positive and negative DC bus K semiconductors connected in series between the interconnection point of the kth (k is a natural number) and (k + 1) th capacitors and the interconnection point of the kth and (k + 1) th semiconductor elements, respectively. Switches in the same direction and even number connected in series between the interconnection points of the nth and (n + 1) th semiconductor elements, both on the positive and negative buses from the middle point of the leg It includes a diode midpoint of the even number of diodes comprises a diode clamp circuit connected to the neutral point of the DC circuit.

It is a figure which shows the structure of the voltage type self-excitation type power converter device which concerns on 1st Embodiment. It is a figure which shows the structure of the power converter device which concerns on 2nd Embodiment. It is a figure which shows the structure of the power converter device which concerns on 3rd Embodiment. It is a figure which shows the structure of the power converter device which concerns on 4th Embodiment. It is a figure which shows the structure of the power converter device which concerns on 5th Embodiment. It is a figure which shows the structure of the power converter device which concerns on 6th Embodiment. It is a figure which shows the structure of the power converter device which concerns on 7th Embodiment. It is a figure which shows the structure of the power converter device which concerns on 8th Embodiment. It is a figure which shows the structure of the power converter device which concerns on 9th Embodiment. It is a figure which shows the structure of the power converter device which concerns on 10th Embodiment. It is a figure which shows the structure of the power converter device which concerns on 11th Embodiment. It is a figure which shows the structure of the power converter device which concerns on 12th Embodiment. It is a figure which shows the structure of the conventional power converter device. It is a figure which shows the other structure of the conventional power converter device.

  Hereinafter, the configuration and operation of the embodiment will be described in detail with reference to the drawings.

[First embodiment]
FIG. 1 is a diagram showing a configuration of a voltage source self-excitation power converter according to the first embodiment. FIG. 1 shows a configuration in which six DC capacitors are connected in series.

  Since the DC voltage as a whole is as high as + 3E and -3E, the number of series of semiconductor elements is determined so as to meet the voltage. The capacitance and rated voltage of each capacitor are the same, and “E” indicates the rated voltage of the capacitor. In FIG. 1, a leg 1 is formed by connecting twelve semiconductor elements 101 to 112 in which switching elements (IGBT and the like) and diodes are connected in antiparallel. In this specification, a circuit element in which the switching element and the diode are connected in antiparallel is referred to as a semiconductor element. The diodes constituting the diode clamp circuit 3 are also configured in series according to the voltage. A single diode having a high voltage rating may be configured.

  By using the leg 1 and the diode clamp circuit 3, it is possible to output three voltage levels of + 3E, 0, and −3E to the AC output terminal U as in the conventional case. However, when viewed from the load, the voltage level change accompanying leg switching becomes as large as 3E, and a voltage surge or the like due to reflection on the cable may occur. That is, the output voltage waveform and the voltage waveform reflected from the load are superimposed to generate an overvoltage, which may increase the stress on the load.

  Therefore, in FIG. 1, the connection point A between the semiconductor elements 101 and 102 and the connection point B between the DC capacitors 201 and 202 are connected by the switch 41, the connection point C ′ between the semiconductor elements 102 and 103, and the DC capacitor. The connection point D between 202 and 203 is connected by a switch 42, the connection point E ′ between the semiconductor elements 110 and 111, and the connection point F between the DC capacitors 204 and 205 are connected by a switch 43. A switch 44 connects the connection point G between 111 and 112 and the connection point H between the DC capacitors 205 and 206. With such a configuration, + 2E, + E, −E, −2E of the DC capacitor voltage E can be generated at the AC output terminal U, which is called + 3E, + 2E, + E, 0, −E, −2E, −3E. A 7-level voltage can be output. Thereby, since the voltage change accompanying switching becomes E, the voltage stress of the load is reduced.

  The 7-level voltage is output as follows. The output of + 3E turns on all the semiconductor elements 101 to 106 and turns off the other semiconductor elements (hereinafter, in order to avoid redundant explanation, only the semiconductor elements or switches that are turned on are shown, and the other semiconductor elements or switches are turned off. The description to be omitted is omitted). The output of + 2E turns on the switch 41 and the semiconductor elements 102 to 106. The output of + E turns on the switch 42 and the semiconductor elements 103 to 106. The output of 0 turns on the semiconductor elements 104 to 109 and connects the neutral point C and the AC output terminal U via the diode clamp circuit 3. The output of −E turns on the switch 43 and the semiconductor elements 107 to 110. The output of −2E turns on the semiconductor elements 107 to 111 and the switch 44. The output of −3E turns on all the semiconductor elements 107 to 112. The switching sequence as described above is performed using a lookup table or the like, and the pulse width is determined using PWM or the like.

  Here, the switches 41 to 44 can be configured by a semiconductor element having the same voltage rating as the semiconductor element constituting the leg and a unidirectional semiconductor element by appropriately selecting a connection point with the leg. That is, for example, when + 3E is output, the collector potential of the switch 41 is + 3E and the emitter potential is + 2E, so that the voltage E is applied between the terminals of the switch 41. Here, since the semiconductor element which comprises the leg can use the voltage E, the same semiconductor element is applicable. Next, when + E is output, the emitter potential of the switch 41 is + 2E, the AC output terminal U is + E, and the switch 41 and the semiconductor element 102 bear a voltage of + E. When 0 is output, the emitter potential of the switch 41 is + 2E, the AC output terminal U is 0, and the switch 41 and the semiconductor elements 102 and 103 bear a voltage of + 2E. In either case, the voltage per semiconductor element is E or less. The same applies to the switches 42 to 44.

  From another point of view, the connection configuration shown in FIG. 1 makes it possible to effectively use the series number of semiconductor elements constituting the leg, that is, to realize a high breakdown voltage and multilevel output.

  In FIG. 1, the number of series is described as 12 because one semiconductor element can handle the corresponding DC capacitor voltage E. The same applies even if the number of series increases further, such as when the DC capacitor voltage is handled in a series configuration of two semiconductor elements. In FIG. 1, the DC voltage level is described as 7. However, a high voltage multi-level power conversion device can be realized with the same idea.

  As described above, in the power conversion device according to the present embodiment, the circuit element formed of the antiparallel connection of the diode and the switching element is a semiconductor element, and there are 2n capacitors 201 to 206 having the same voltage rating (n = n in FIG. 1). 3) a DC circuit 2 connected in series, and a series circuit in which a plurality of 4n semiconductor elements having the same voltage rating are connected in series, the leg 1 being connected in parallel with the DC circuit by positive and negative buses; , The k-th (k is a natural number) and (k + 1) th capacitor interconnection point counted from the positive and negative DC buses P and N, and the kth and (k + 1) th semiconductor element interconnection point The switches 41 to 44 composed of k semiconductor elements connected in series between the n-th and (n + 1) th semiconductor elements are connected to the positive and negative buses from the middle point of the leg. Series connection between It includes the same direction and an even number of diodes 301 to 306 which is the midpoint of the even number of diodes comprises a diode clamp circuit 3 connected to the neutral point C of the DC circuit.

(effect)
According to this embodiment, not only the voltage handled by the power converter can be increased, but also the output voltage level can be increased, and a power converter capable of smoother voltage output can be provided.

[Second Embodiment]
(Constitution)
FIG. 2 is a diagram illustrating a configuration of the power conversion device according to the second embodiment. In this embodiment, a neutral point switch 6 is used instead of the diode clamp circuit 3 of FIG.

  Unlike the prior art, the neutral point switch 6 is composed of a series connection of switches 61 and 62 because the DC voltage to be handled is high. The switches 61 and 62 are composed of semiconductor elements 61A and 61B and 62A and 62B, respectively. As these semiconductor elements, semiconductor elements having the same voltage rating as the semiconductor elements constituting the legs can be applied.

(Function)
FIG. 2 shows a configuration in which four DC capacitors are connected in series. Since the DC voltage as a whole is as high as + 2E and -2E, the series number of semiconductor elements is determined so as to meet the voltage. In FIG. 2, the leg 1 is configured by connecting eight semiconductor elements 101 to 108 in series. A connection point I between the semiconductor elements 101 and 102, a connection point J between the DC capacitors 201 and 202 are connected by a switch 41, a connection point K between the semiconductor elements 107 and 108, and a connection point between the DC capacitors 203 and 204. L is connected by a switch 42. The output of + 2E turns on all the semiconductor elements 101 to 104. The output of + E turns on the switch 41 and the semiconductor elements 102 to 104. An output of 0 turns on the neutral point switch 6. The output of −E turns on the semiconductor elements 105 to 107 and the switch 42. The output of −2E turns on all the semiconductor elements 105 to 108.

  By connecting the switches to the locations shown in FIG. 2, the switches can be configured with unidirectional semiconductor elements like the switches 41 and 42, and the series number of semiconductor elements forming the legs can be effectively utilized.

  As described above, in the power conversion device according to the present embodiment, the circuit element formed of the anti-parallel connection of the diode and the switching element is a semiconductor element, and 2n capacitors 201 to 204 having the same voltage rating (n is a natural number) are connected in series. A DC circuit 2 connected, and a series circuit in which 4n semiconductor elements 101 to 108 having the same voltage rating are connected in series, the leg 1 being connected in parallel with the DC circuit by positive and negative buses; , The neutral point switch 6 connected between the neutral point of the DC circuit 2 and the midpoint of the leg and connected in series with 2n semiconductor elements having the same voltage rating, and the positive and negative DC buses P, N K connected in series between the interconnection point of the kth (k = 1 in this example) and (k + 1) th capacitors and the interconnection point of the kth and (k + 1) th semiconductor elements. With one semiconductor element Comprising a capacitor leg between switches 41 and 42 has been made.

(effect)
According to the second embodiment, it is possible not only to increase the voltage handled by the power converter, but also to increase the output voltage level and to provide a power converter that can output a smoother voltage.

  In addition, FIG. 2 shows an example in which the neutral point switches 61 and 62 are configured by the reverse series connection of the IGBT. However, a semiconductor element (for example, a series circuit of an IGBT and a diode) that can prevent the reverse direction is reversed in the current direction. May be connected in parallel, or may be another equivalent circuit configuration such as a combination of a diode bridge and an IGBT.

[Third embodiment]
(Constitution)
FIG. 3 is a diagram illustrating a configuration of a power conversion device according to the third embodiment. The present embodiment is another configuration in which a neutral point switch 6 is used instead of the diode clamp circuit of FIG.

  Unlike the configuration of FIG. 12 described above, the neutral point switch 6 includes a series connection of switches 61, 62, and 63 because the DC voltage to be handled is high. The configuration of the switch is the same as in FIG.

(Function)
In FIG. 3, when 0 is output to the AC voltage output terminal U, the neutral point switch 6 is turned on, which is different from the case of FIG. 1, but the other operations and actions are the same as those of the circuit of FIG.

  Similar to the example of FIG. 1, by connecting the switches 41 and 44 to the locations shown in FIG. 3, the switch can be configured with a unidirectional semiconductor element, and the series number of semiconductor elements constituting the leg can be effectively utilized. It is.

(effect)
According to the third embodiment, as in the embodiment of FIG. 1, not only the voltage handled by the power converter is further increased, but also the output voltage level can be increased, and power conversion capable of smoother voltage output is possible. Equipment can be provided.

  2 and 3, the DC voltage level is described as being at the 5th level and the 7th level. However, a power converter having a higher voltage and multilevel can be realized with the same idea.

[Fourth embodiment]
(Constitution)
FIG. 4 is a diagram illustrating a configuration of a power conversion device according to the fourth embodiment.

  In order to handle a high voltage, the above-mentioned leg of the voltage source converter and the neutral point switch of FIG. 14 are configured by connecting a plurality of semiconductor elements in series. In consideration of economy, semiconductor devices having the same rated voltage and rated current are used. Further, since the DC circuit also has a high voltage, it is configured by connecting DC capacitors in series. Further, in this configuration, the connection points M and N between the semiconductor elements constituting the leg and the connection point O between the neutral point switches are connected by the capacitors 7 and 8, respectively.

(Function)
The operation will be described with reference to FIG.

  FIG. 4 shows a configuration in which four DC capacitors are connected in series.

  Since the DC voltage as a whole is as high as + 2E and -2E, the series number of semiconductor elements is determined so as to meet the voltage. In FIG. 4, the leg 1 is configured by serially connecting eight semiconductor elements 101 to 108. The switches constituting the neutral point switch 6 are also configured in series according to the voltage. The configuration of the switch is the same as in FIG.

  By using the leg 1 and the neutral point switch 6, three voltage levels of + 2E, 0, and −2E can be output to the AC output terminal U as in the conventional example. However, when viewed from the load, the change in the voltage level due to the switching of the leg becomes as large as 2E, and there is a possibility that the stress is increased for the load such as a voltage surge due to reflection on the cable.

  Therefore, in FIG. 4, the connection point M between the semiconductor elements 101 and 102 and the connection point O between the neutral point switches 61 and 62 are connected by the capacitor 7, and the connection point N ′ between the semiconductor elements 107 and 108 is connected. A capacitor 8 connects between the connection points O between the neutral point switches 61 and 62. By adopting such a configuration and setting the voltages of the capacitors 7 and 8 to E, a DC capacitor voltage E or -E can be generated at the AC output terminal U, and five levels of + 2E, + E, 0, -E, and -2E. Can be output. Thereby, since the voltage change accompanying switching becomes E, the voltage stress of the load is reduced. Note that the voltage + E of the capacitor 7 and the voltage -E of the capacitor 8 are charged when the apparatus is activated.

  The 5-level voltage output is performed as follows.

  The output of + 2E turns on all the semiconductor elements 101 to 104. There are two + E outputs. That is, the neutral point switch 61 and the semiconductor elements 102, 103, and 104 are turned on. Alternatively, the semiconductor element 101 and the neutral point switch 62 are turned on. An output of 0 turns on both neutral point switches 61 and 62. There are two outputs of -E. That is, the neutral point switch 61 and the semiconductor elements 105, 106, and 107 are turned on. Alternatively, the semiconductor element 108 and the neutral point switch 62 are turned on. The output of + 2E turns on all the semiconductor elements 105 to 108.

  In addition, by connecting capacitors to the points M, N, and O shown in FIG. 4, the number of series semiconductor elements constituting the leg can be effectively utilized. For example, when −2E is output, the potential of the AC output terminal U is −2E. At this time, the potential at the point M connecting the capacitor 7 is + E, and the potential difference is 3E, but three semiconductor elements 102, 103, and 104 are connected in series between the two points. Since the voltage E can be handled by one semiconductor element, a voltage of 3E can be handled by three series, and there is no problem.

  In FIG. 4, the number of series of semiconductor elements is described as eight, but the same applies even if the number of series is further increased.

  As described above, in the power conversion device according to the present embodiment, the circuit element including the anti-parallel connection of the diode and the switching element is a semiconductor element, and there are 2n DC capacitors 201 to 204 having the same voltage rating (n is a natural number). A DC circuit 2 connected in series and a series circuit in which 4n semiconductor elements 101 to 108 having the same voltage rating are connected in series, and connected in parallel to the DC circuit by positive and negative buses P and N. A neutral point switch 6 connected between the neutral point of the DC circuit 2 and the neutral point of the DC circuit 2 and connected in series with 2n semiconductor elements having the same voltage rating, and the positive bus of the leg Leg-switch first capacitor 7 connected between the connection point between the kth (k is a natural number) and k + 1th semiconductor elements from P and the connection point between the semiconductor elements constituting the neutral point switch 6. , Between the leg and switch connected between the connection point between the kth and k + 1th semiconductor elements from the negative bus N of the leg 1 and the connection point between the semiconductor elements constituting the neutral point switch 6 And a second capacitor 8.

(effect)
According to the fourth embodiment, as in the other examples, the power converter that not only increases the voltage handled by the power converter, but also increases the output voltage level and enables smoother voltage output. Can be provided.

[Fifth Embodiment]
(Constitution)
FIG. 5 is a diagram illustrating a configuration of a power conversion device according to the fifth embodiment. Although this embodiment is the same as that of FIG. 4, it is the structure from which the leg side connection point of a capacitor | condenser differs.

  The capacitor 7 is connected between the connection point P ′ of the semiconductor elements 102 and 103 and the connection point O of the neutral point switches 61 and 62, and the capacitor 8 is connected to the connection point Q of the semiconductor elements 106 and 107 and the neutral point switches 61 and 62. Connected between points O.

(Function)
Even with such a configuration, the same operation as in FIG. 4 can be realized.

(effect)
In addition, even with such a configuration, the same effect as in FIG. 4 can be obtained.

[Sixth Embodiment]
(Constitution)
FIG. 6 is a diagram illustrating a configuration of a power conversion device according to the sixth embodiment. The present embodiment is the same as that of FIG. 5 except that a diode clamp circuit 3 is provided instead of the neutral point switch 62.

(Function)
Even with such a configuration, the same operation as in FIG. 5 can be realized.

(Effect of Example)
Also, with this configuration, the same effect as in FIG. 5 can be obtained.

[Seventh embodiment]
(Constitution)
FIG. 7 is a diagram illustrating a configuration of a power conversion device according to the seventh embodiment. This embodiment is the same as that of FIG. 4, but uses six DC capacitors and further increases the DC voltage to be handled. Therefore, the neutral point switch 6 is composed of a series connection of switches 61, 62 and 63. . The configuration of the switch is the same as in FIG.

  Capacitors 9, 10 and 11, 12 are two in series in order to handle a voltage of 2E. Capacitors 9 and 10 are connected between the connection point R of the semiconductor elements 101 and 102 and the connection point S of the neutral point switches 61 and 62, and the capacitor 7 is connected between the connection point T of the semiconductor elements 102 and 103 and the neutral point switches 62 and 63. Between the connection point U ′, the capacitor 8 is connected between the connection point V of the semiconductor elements 110 and 111 and the connection point U ′ of the neutral point switches 62 and 63, and the capacitors 11 and 12 are connected to the connection point W of the semiconductor elements 111 and 112. Connected between the connection points S of the neutral point switches 61 and 62.

  If this configuration is used, + 7E, + 2E, + E, 0, -E, -2E, and -3E can be output at seven levels. With the connection configuration shown in FIG. 7, the number of semiconductor elements that form the leg can be used effectively as in the case of FIG. 5.

(Function)
7 is different from the case of FIG. 4 in that the output level is 7 levels, but other operations and actions are the same as those of the circuit of FIG.

(effect)
According to the present embodiment, as in the embodiment of FIG. 3, not only the voltage handled by the power converter can be further increased, but also the output voltage level can be increased and a smoother voltage output is possible. Can provide.

[Eighth embodiment]
(Constitution)
FIG. 8 is a diagram illustrating a configuration of a power conversion device according to the eighth embodiment. The configuration of the present embodiment is the same as that of FIG. 6, but the configuration is different in the connection point on the leg side of the capacitor.

  Capacitors 9 and 10 are connected between the connection point T of the semiconductor elements 102 and 103 and the connection point S of the neutral point switches 61 and 62, and the capacitor 7 is connected between the connection point X of the semiconductor elements 104 and 105 and the neutral point switches 62 and 63. Connected between connection points U ′. The capacitor 8 is between the connection point Y of the semiconductor elements 108 and 109 and the connection point U ′ of the neutral point switches 62 and 63, and the capacitors 11 and 12 are the connection point V of the semiconductor elements 110 and 111 and the neutral point switches 61 and 62. Are connected between the connection points S.

(Function)
Even with such a configuration, the same operation as in FIG. 7 can be realized.

  The connection on the leg side of the capacitor may be a connection configuration other than the connections shown in FIGS. 6 and 7 as long as it does not overlap between a plurality of capacitors.

  That is, in the power conversion device according to the present embodiment, the neutral point switch 6 is configured by serial connection of 2n (n is a natural number) semiconductor elements having the same current voltage rating (same rating), and the leg has a plurality of the same rating. When the semiconductor element is configured by 4n series connections, the first terminal of the capacitor is connected to the interconnection point of the 2kth and (2k + 1) th semiconductor elements counted from the DC neutral point C. In this case, the k-th and (k + 1) -th semiconductor element interconnection points counting from the positive and negative DC buses of the leg 1 (FIG. 7), or the 2k-th counting from the positive and negative DC buses of the leg 1 And a second terminal of the capacitor is connected between the (2k + 1) th semiconductor element interconnection point (FIG. 8).

(effect)
Even with the configuration as shown in FIG. 8, the same effect as in FIG. 7 can be obtained.

[Ninth Embodiment]
(Constitution)
FIG. 9 is a diagram illustrating a configuration of a power conversion device according to the ninth embodiment. This embodiment is the same as that of FIG. 4, but shows an advantageous configuration when a structure in which a set in which two semiconductor elements are connected in series in the same direction is accommodated in one package is applied.

  In this example, the neutral point switch 6 is different from FIG. 2 and the like, and the series semiconductor configurations 64 and 65 are each configured by connecting two semiconductor elements in the same direction in series, and the series semiconductor configurations 64 and 65 are connected in opposite directions. The difference is that the configuration is connected in series. Each of the series semiconductor structures 64 and 65 includes a series connection of semiconductor elements 641 and 642 and a series connection of semiconductor elements 651 and 652. Like the neutral switch, the leg 1 can also be configured using a series semiconductor configuration in which two semiconductor elements are connected in series.

  9, the neutral point switch side terminal of the capacitor 7 is connected to the connection point a of the semiconductor elements 641 and 642 in order to perform the same operation as in FIG. The neutral point switch side terminal of the capacitor 8 is connected to the connection point b of the semiconductor elements 651 and 652.

  With the connection configuration shown in FIG. 9, the leg and the neutral point switch can be configured by semiconductor elements having the same configuration.

(Function)
In FIG. 9, when outputting + 2E, 0, and −2E, the same control as in FIG. 4 may be performed.

  However, when outputting + E, the semiconductors 642 and 102 to 104 in the neutral point switch are turned on, or the semiconductor element 101 and the semiconductor elements 641, 651, and 652 are turned on. When outputting -E, the semiconductor elements 641, 642, 651 and the semiconductor element 105 are turned on, or the semiconductor elements 106 to 108 and the semiconductor element 652 are turned on.

(effect)
According to the present embodiment, the same effects as those of the example of FIG. 4 can be obtained, and the leg and the neutral point can be configured by semiconductor elements having the same configuration, and a more economical power conversion device can be provided.

[Tenth embodiment]
(Constitution)
FIG. 10 is a diagram illustrating a configuration of a power conversion device according to the tenth embodiment. Although this embodiment has the same configuration as that of FIG. 9, the connection point on the leg side of the capacitor is different.

  The capacitor 7 is connected between the connection point c ′ of the semiconductor elements 102 and 103 and the connection point a of the neutral point switches 641 and 642, and the capacitor 8 is connected between the connection point d of the semiconductor elements 106 and 107 and the neutral point switches 651 and 652. Connected between points b.

(Function)
Even with such a configuration, the same operation as in FIG. 9 can be realized.

  The connections on the leg side of the capacitors may be other connection combinations than those shown in FIGS. 9 and 10 as long as they do not overlap among a plurality of capacitors.

(effect)
Even with such a configuration, the same effect as in FIG. 9 can be obtained.

  4 to 10, the DC voltage level has been described as being at the 5th level and the 7th level, but a higher voltage power conversion device can be realized with the same idea.

[Eleventh embodiment]
(Constitution)
FIG. 11 is a diagram illustrating the configuration of the power conversion device according to the eleventh embodiment. In this embodiment, a connection point between semiconductor elements constituting a leg and a connection point between neutral point switches are connected by a capacitor. FIG. 11 shows a configuration in which four DC capacitors are connected in series.

(Function)
Since the DC voltage as a whole is as high as + 2E and -2E, the series number of semiconductor elements is determined so as to meet the voltage. In FIG. 11, leg 1 is configured by serially connecting eight semiconductor elements 101 to 108. Switches 41 and 42 are provided at the positions shown in FIG. 11 to connect between the series capacitor 2 and the leg 1. Further, capacitors 7 and 8 are provided, and the switches 41 and 42 and the leg 1 are connected.

  By using the leg 1 and the switches 41 and 42, three voltage levels of + 2E, 0, and −2E can be output to the AC output terminal U as in the conventional example. By charging E to the voltage of the capacitors 7 and 8, the output of + E turns on the semiconductor elements 101, 412, 103, and 104. Alternatively, the semiconductor elements 411, 102, 103, and 104 are turned on. Similarly, the output of -E turns on 108, 422, 106, 105 or 421, 107, 106, 105. As a result, a DC capacitor voltage E or -E is generated at the AC output terminal U, and five levels of voltages + 2E, + E, 0, -E, and -2E can be output.

  As described above, in the power conversion device according to the present embodiment, the circuit element including the anti-parallel connection of the diode and the switching element is a semiconductor element, and there are 2n DC capacitors 201 to 204 having the same voltage rating (n is a natural number). A DC circuit 2 connected in series and a series circuit in which 4n semiconductor elements 101 to 108 having the same voltage rating are connected in series, and connected in parallel with the DC circuit 2 by positive and negative buses P and N And connected between the neutral point C of the DC circuit 2 and the connection point f between the kth (k is a natural number) and k + 1th semiconductor elements from the positive bus P of the leg, A first switch 41 in which n semiconductor elements are connected in series; a semiconductor element interconnection point g of the first switch 41; and a kth and a k−1th semiconductor element from the positive bus P of the leg. Connection point e A first capacitor 7 connected in between, a neutral point C of the DC circuit, and a connection point h between the kth and k + 1th semiconductor elements from the negative bus N of the leg, A second switch 42 in which n elements are connected in series, a semiconductor element interconnection point i of the second switch 42, and a connection between the kth and k−1th semiconductor elements from the negative bus N of the leg. And a second capacitor 8 connected between the point j.

(effect)
According to the present embodiment, as in the other embodiments, not only the voltage handled by the power converter is increased, but also the output voltage level can be increased, and a power conversion device capable of smoother voltage output is provided. it can.

[Twelfth embodiment]
(Constitution)
FIG. 12 is a diagram illustrating a configuration of a power conversion device according to the twelfth embodiment. This embodiment has the same configuration as that of FIG. 11, but uses six DC capacitors and further increases the DC voltage to be handled. Therefore, twelve semiconductor elements of leg 1 are connected in series. The switches 41 and 42 are composed of semiconductor elements 411, 412, 413, 421, 422, and 423. Further, capacitors 7 and 8 are provided, and the switches 41 and 42 and the leg 1 are connected.

  If this configuration is used, + 7E, + 2E, + E, 0, -E, -2E, and -3E can be output at seven levels.

(Function)
By using the leg 1 and the switches 41 and 42, three voltage levels of + 3E, 0, and −3E can be output to the AC output terminal U. By setting the voltage of the capacitors 7 and 8 to E, the output of + 2E turns on the semiconductor elements 101, 102, 413, 104, 105, and 106. The output of + E turns on the semiconductor elements 411, 412, 103, 104, 105, and 106. Similarly, the output of −E turns on the semiconductor elements 421, 422, 110, 109, 108, and 107, and the output of −2E turns on the semiconductor elements 112, 111, 423, 109, 108, and 107. As a result, 7-level voltages of + 3E, + 2E, + E, 0, −E, −2E, and −3E can be output to the AC output terminal U.

(Effect of Example)
According to the present invention, as in the embodiment of FIG. 11, not only can the voltage handled by the power converter be further increased, but also the output voltage level can be increased and a power converter capable of smoother voltage output is provided. Can be provided. In the example of FIG. 12, the number of series of semiconductor elements has been described as twelve, but the same applies even if the number of series is further increased.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Leg, 2 ... DC circuit, 3 ... Diode clamp circuit, 6 ... Neutral point switch, 141-44 ... Switch

Claims (8)

A circuit element consisting of an anti-parallel connection of a diode and a switching element is configured as a semiconductor element,
A DC circuit in which 2n capacitors (n is a natural number) of the same voltage rating are connected in series;
A series circuit in which a plurality of 4n semiconductor devices having the same voltage rating are connected in series, the legs being connected in parallel with the DC circuit by positive and negative buses;
A series connection is made between the interconnection point of the kth (k + 1) th capacitor and the interconnection point of the kth and (k + 1) th semiconductor elements, counting from the positive and negative DC buses, respectively. A switch composed of k semiconductor elements connected to
Including in the same direction and an even number of diodes connected in series between the interconnection points of the nth and (n + 1) th semiconductor elements on the positive and negative bus side from the midpoint of the leg, A diode clamp circuit in which a midpoint is connected to a neutral point of the DC circuit;
A voltage-type self-excited power conversion device comprising:   2. The power converter according to claim 1, wherein the semiconductor elements constituting the legs and the switches have the same voltage rating, and unidirectional semiconductor elements including IGBTs are used as the semiconductor elements. A circuit element consisting of an anti-parallel connection of a diode and a switching element is configured as a semiconductor element,
A DC circuit in which 2n capacitors (n is a natural number) of the same voltage rating are connected in series;
A series circuit in which a plurality of 4n semiconductor devices having the same voltage rating are connected in series, the legs being connected in parallel with the DC circuit by positive and negative buses;
A neutral point switch connected between a neutral point of the DC circuit and a midpoint of the leg, and 2n semiconductor elements having the same voltage rating connected in series;
A series connection is made between the interconnection point of the kth (k + 1) th capacitor and the interconnection point of the kth and (k + 1) th semiconductor elements, counting from the positive and negative DC buses, respectively. A capacitor-leg switch composed of k semiconductor elements connected to
A voltage-type self-excited power conversion device comprising:   4. The semiconductor elements constituting the leg, the neutral point switch and the capacitor-leg switch have the same voltage rating, and a unidirectional semiconductor element including an IGBT is used as each semiconductor element. The power converter described. A circuit element consisting of an anti-parallel connection of a diode and a switching element is configured as a semiconductor element,
A DC circuit in which a plurality of DC capacitors having the same voltage rating are connected in series (n is a natural number);
A series circuit in which a plurality of 4n semiconductor devices having the same voltage rating are connected in series, the legs being connected in parallel with the DC circuit by positive and negative buses;
A neutral point switch connected between a neutral point of the DC circuit and a midpoint of the leg, and 2n semiconductor elements having the same voltage rating connected in series;
Both the kth (k is a natural number) and k + 1th semiconductor element connection points from the positive and negative buses of the leg and the connection points of the semiconductor elements constituting the neutral switch are connected. First and second capacitors between the legs and the switches;
A voltage-type self-excited power conversion device comprising:   The neutral point switch is characterized in that one or more series circuits of two semiconductor elements in different directions are connected in series, and the neutral point switch side connection points of the first and second capacitors are the same. The power conversion device according to claim 5.   The neutral point switch is characterized in that one or more series circuits of two semiconductor elements in the same direction are connected in series, and the neutral point switch side connection points of the first and second capacitors are different from each other. The power conversion device according to claim 5. A circuit element consisting of an anti-parallel connection of a diode and a switching element is configured as a semiconductor element,
A DC circuit in which a plurality of DC capacitors having the same voltage rating are connected in series (n is a natural number);
A series circuit in which a plurality of 4n semiconductor devices having the same voltage rating are connected in series, the legs being connected in parallel with the DC circuit by positive and negative buses;
Connected between the neutral point of the DC circuit and the connection point between the kth (k is a natural number) and the k + 1th semiconductor elements counted from the positive bus of the leg, and n semiconductor elements are connected in series. A first switch,
A first capacitor connected between a semiconductor element interconnection point of the first switch and a k-th and k−1th semiconductor element interconnection point from the positive bus of the leg;
A second switch connected between a neutral point of the DC circuit and a connection point between the kth and k + 1th semiconductor elements counted from the negative bus of the leg, and n semiconductor elements connected in series When,
A second capacitor connected between a semiconductor element interconnection point of the second switch and a k-th and k−1th semiconductor element interconnection point from the negative bus of the leg;
A voltage-type self-excited power conversion device comprising:

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