Inverter device and inverter module

Abstract

To improve efficiency in an inverter device of a single-phase three-wire system.SOLUTION: An inverter device converts an input DC power into an AC power of a single-phase three-wire system and outputs the converted power, and comprises: a first phase output terminal, a second phase output terminal, and a neutral output terminal; an inverter unit that converts a DC power into an AC power; a first phase power line that connects the inverter unit and the first phase output terminal to each other and is supplied with a first phase power of the AC power; a second phase power line that connects the inverter unit and the second phase output terminal to each other and is supplied with a second phase power of the AC power; a neutral power line that connects the inverter unit and the neutral output terminal to each other; a first short circuit that is connected between the first phase power line and the neutral power line and can short-circuit between the first phase power line and the neutral power line; a second short circuit that is connected between the second phase power line and the neutral power line and can short-circuit between the second phase power line and the neutral power line; and a control unit that controls the inverter unit, first short circuit, and second short circuit.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an inverter device and an inverter module. [Background technology]

[0002] 2. Description of the Related Art Conventionally, a single-phase two-wire inverter device is known as an inverter device that converts DC power into AC power.

[0003] As a means for improving the efficiency of such a single-phase two-wire inverter device, it has been proposed to provide a short-circuitable circuit called a HERIC circuit between the output lines (see, for example, Patent Document 1).

[0004] On the other hand, high efficiency is also required in single-phase three-wire inverter devices. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] DE 102008048841 A1 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above problems, and has an object to achieve high efficiency in a single-phase three-wire inverter device. [Means for solving the problem]

[0007] To solve the above problems, the present invention provides: An inverter device that converts input DC power into single-phase three-wire AC power and outputs the AC power, a first phase output terminal, a second phase output terminal, and a neutral output terminal; an inverter unit that converts the DC power into the AC power; a first-phase power line connecting the inverter unit and the first-phase output terminal and through which first-phase power of the AC power is supplied; a second-phase power line connecting the inverter unit and the second-phase output terminal and through which second-phase power of the AC power is supplied; a neutral power line connecting the inverter unit and the neutral output terminal; a first short circuit connected between the first phase power line and the neutral power line and capable of short-circuiting the first phase power line and the neutral power line; a second short circuit connected between the second phase power line and the neutral power line and capable of short-circuiting the second phase power line and the neutral power line; The power supply device is characterized by comprising a control unit that controls the inverter unit, the first short circuit, and the second short circuit.

[0008] According to the present invention, in a single-phase three-wire inverter device, high efficiency can be achieved by providing a first short-circuit connected between a first-phase power line and a neutral power line and capable of short-circuiting between the first-phase power line and the neutral power line, and a second short-circuit connected between a second-phase power line and the neutral power line and capable of short-circuiting between the second-phase power line and the neutral power line.

[0009] In the present invention, The inverter unit is A positive input terminal connected to a positive terminal of a DC power supply and a negative input terminal connected to a negative terminal of the DC power supply are connected in parallel. a first phase leg in which a first switching element connected to the positive input terminal and a second switching element connected to the negative input terminal are connected in series; a neutral leg in which a third switching element connected to the positive input terminal and a fourth switching element connected to the negative input terminal are connected in series; a second phase leg in which a fifth switching element connected to the positive input terminal and a sixth switching element connected to the negative input terminal are connected in series; having the first phase leg has a first phase connection point to which the first phase power line is connected, at a midpoint between the first switching element and the second switching element; the neutral leg has a neutral connection point to which the neutral power line is connected at a midpoint between the third switching element and the fourth switching element, The second phase leg may have a second phase connection point, to which the second phase power line is connected, at a midpoint between the fifth switching element and the sixth switching element.

[0010] In this way, high efficiency can be achieved in a three-arm inverter device having a first phase leg, a second phase leg, and a neutral leg.

[0011] In the present invention, The inverter section is A positive input terminal connected to a positive terminal of a DC power supply and a negative input terminal connected to a negative terminal of the DC power supply are connected in parallel. a first phase leg in which a first switching element connected to the positive input terminal and a second switching element connected to the negative input terminal are connected in series; a neutral point circuit in which a first constant voltage source connected to the positive input terminal and a second constant voltage source connected to the negative input terminal are connected in series; a second phase leg in which a fifth switching element connected to the positive input terminal and a sixth switching element connected to the negative input terminal are connected in series; having the first phase leg has a first phase connection point to which the first phase power line is connected, at a midpoint between the first switching element and the second switching element; the neutral point circuit has a neutral connection point to which the neutral power line is connected at a midpoint between the first constant voltage source and the second constant voltage source, The second phase leg may have a second phase connection point, to which the second phase power line is connected, at a midpoint between the fifth switching element and the sixth switching element.

[0012] This makes it possible to achieve high efficiency in a midpoint split type inverter device in which the input voltage determines the potential of the neutral power line by two constant voltage sources connected in parallel between the input terminals.

[0013] In the present invention, the first short circuit includes a first short-circuit switching element that switches on and off a current flowing from the neutral power line side to the first phase power line side, and a second short-circuit switching element that switches on and off a current flowing from the first phase power line side to the neutral power line side, the second short circuit includes a third short-circuit switching element that switches on and off a current flowing from the second phase power line side to the neutral power line side, and a fourth short-circuit switching element that switches on and off a current flowing from the neutral power line side to the second phase power line side, The control unit controls the frequency of the AC power to be output in either half cycle of the frequency of the AC power to be output. The PWM control of the first switching element to the sixth switching element is turning on the first switching element and turning off the second switching element; turning off the third switching element and turning on the fourth switching element; turning off the fifth switching element and turning on the sixth switching element; turning on the first short-circuit switching element; a first mode in which the third short-circuit switching element is turned on; turning on the first switching element and turning off the second switching element; turning on the third switching element and turning off the fourth switching element; turning off the fifth switching element and turning on the sixth switching element; turning on the first short-circuit switching element; a second mode in which the third short-circuit switching element is turned on; turning off the first switching element and the second switching element; turning off the third switching element and the fourth switching element; turning off the fifth switching element and the sixth switching element; turning on the first short-circuit switching element; a third mode in which the third short-circuit switching element is turned on; and may include control of repeating transition in the order of the first mode, the second mode, and the third mode.

[0014] According to this, in the third mode in which the first short circuit and the second short circuit are shorted, the third switching element and the fourth switching element of the neutral leg are turned off, so that the potential of the neutral power line connecting the first short circuit and the second short circuit becomes the midpoint of the input voltage, thereby making it possible to avoid generation of noise due to fluctuations in this potential. One half cycle of the frequency of the AC power to be output may be the first half cycle or the second half cycle.

[0015] In the present invention, The PWM control of the first switching element to the sixth switching element by the control unit in the other half cycle of the frequency of the AC power to be output is In the first mode and the second mode, The first switching element and the fifth switching element are switched on and off, The second switching element and the sixth switching element are switched on and off, The third switching element and the fourth switching element are switched on and off, turning on the second short-circuit switching element; a 1-2 mode and a 2-2 mode in which the fourth short-circuit switching element is turned on; turning off the first switching element and the second switching element; turning off the third switching element and the fourth switching element; turning off the fifth switching element and the sixth switching element; turning on the second short-circuit switching element; a 3-2 mode in which the fourth short-circuit switching element is turned on; and may include control for repeating transition in the order of the 1-2 mode, the 2-2 mode, and the 3-2 mode.

[0016] According to this, in the 3-2 mode in which the first short circuit and the second short circuit are shorted, the third switching element and the fourth switching element of the neutral leg are turned off, so that the potential of the neutral power line connecting the first short circuit and the second short circuit becomes the midpoint of the input voltage, and therefore it is possible to avoid the generation of noise due to fluctuations in this potential. The other half cycle is the latter half cycle if one half cycle is the first half cycle, and is the first half cycle if one half cycle is the second half cycle.

[0017] In the present invention, the first short circuit includes a first short-circuit switching element that switches on and off a current flowing from the neutral power line side to the first phase power line side, and a second short-circuit switching element that switches on and off a current flowing from the first phase power line side to the neutral power line side, the second short circuit includes a third short-circuit switching element that switches on and off a current flowing from the second phase power line side to the neutral power line side, and a fourth short-circuit switching element that switches on and off a current flowing from the neutral power line side to the second phase power line side, The PWM control of the first switching element to the sixth switching element by the control unit in one half cycle of the frequency of the AC power to be output is turning on the first switching element and turning off the second switching element; turning off the third switching element and turning on the fourth switching element; turning off the fifth switching element and turning on the sixth switching element; turning on the first short-circuit switching element; a fourth mode in which the third short-circuit switching element is turned on; turning on the first switching element and turning off the second switching element; turning on the third switching element and turning off the fourth switching element; turning off the fifth switching element and turning on the sixth switching element; turning on the first short-circuit switching element; a fifth mode in which the third short-circuit switching element is turned on; turning off the first switching element and turning on the second switching element; turning on the third switching element and turning off the fourth switching element; turning on the fifth switching element and turning off the sixth switching element; turning on the first short-circuit switching element; a sixth mode in which the third short-circuit switching element is turned on; turning off the first switching element and turning on the second switching element; turning off the third switching element and turning on the fourth switching element; turning on the fifth switching element and turning off the sixth switching element; turning on the first short-circuit switching element; a seventh mode in which the third short-circuit switching element is turned on; and may include control of repeating transition in the order of the fourth mode, the fifth mode, the sixth mode, and the seventh mode.

[0018] According to this, in the sixth mode and the seventh mode in which the first short circuit and the second short circuit are shorted, the neutral leg is operated and either the third switching element or the fourth switching element is turned on, so that it is possible to avoid a decrease in the modulation rate caused by stopping the neutral leg. One half cycle of the frequency of the AC power to be output may be the first half cycle or the second half cycle.

[0019] In the present invention, The PWM control of the first switching element to the sixth switching element by the control unit in the other half cycle of the frequency of the AC power to be output is In the fourth mode, the fifth mode, the sixth mode, and the seventh mode, The first switching element and the fifth switching element are switched on and off, The third switching element and the fourth switching element are switched on and off, The second switching element and the sixth switching element are switched on and off, turning on the second short-circuit switching element; The power supply may include a 4-2 mode, a 5-2 mode, a 6-2 mode, and a 7-2 mode in which the fourth short-circuit switching element is turned on, and may include control for repeating transitions in the order of the 4-2 mode, the 5-2 mode, the 6-2 mode, and the 7-2 mode.

[0020] According to this, the 6-2 and 7-2 modes in which the first and second short circuits are shorted In this mode, the neutral leg is operated and either the third switching element or the fourth switching element is turned on, so that it is possible to avoid a decrease in modulation rate caused by stopping the neutral leg. If one half cycle is the first half cycle, the other half cycle is the second half cycle, and if one half cycle is the second half cycle, the other half cycle is the first half cycle.

[0021] In the present invention, the first switching element and the second switching element; The first short circuit; A first single-phase two-wire inverter module including: the fifth switching element and the sixth switching element; the second short circuit; a second single-phase two-wire inverter module including: Including, At least one of the first single-phase two-wire inverter module and the second single-phase two-wire inverter module may include the third switching element and the fourth switching element.

[0022] According to this, a three-arm type single-phase three-wire inverter device can be constructed using two single-phase two-wire inverter modules with short circuits, which reduces variation in characteristics, improves heat dissipation, and makes it easier to assemble the inverter device.

[0023] In the present invention, a third leg in which a third switching element connected to the positive input terminal and a fourth switching element connected to the negative input terminal are connected in series; the third leg has a second neutral connection point connected to the neutral connection point at a midpoint between the third switching element and the fourth switching element; the first switching element and the second switching element; The first short circuit; a third single-phase two-wire inverter module including: the fifth switching element and the sixth switching element; the second short circuit; A fourth single-phase two-wire inverter module including: Including, Either the third single-phase two-wire inverter module or the fourth single-phase two-wire inverter module may include the third switching element and the fourth switching element.

[0024] According to this, a midpoint-split type single-phase three-wire inverter device can be constructed using two single-phase two-wire inverter modules with short circuits, which reduces variation in characteristics, improves heat dissipation, and makes it easier to assemble the inverter device.

[0025] In the present invention, The control unit is turning off the third switching element and the fourth switching element of the neutral leg; The inverter may have a mode in which the first switching element and the second switching element of the first phase leg and the fifth switching element and the sixth switching element of the second phase leg are PWM controlled.

[0026] According to this, by using a single-phase three-wire inverter device as a single-phase two-wire inverter device, as in the case of grid-connected operation, it is possible to realize high efficiency of the single-phase two-wire inverter device.

[0027] In the present invention, a third short circuit connected between the first-phase power line and the second-phase power line and capable of short-circuiting the first-phase power line and the second-phase power line; The control unit may be configured to control the third short circuit.

[0028] According to this, by providing a third short circuit capable of short circuiting between the first phase power line and the second phase power line, efficiency is improved compared to a configuration in which a short circuit between the first phase power line and the second phase power line is achieved via the first short circuit and the second short circuit.

[0029] In the present invention, The inverter unit is A positive input terminal connected to a positive terminal of a DC power supply and a negative input terminal connected to a negative terminal of the DC power supply are connected in parallel. a first phase leg in which a first switching element connected to the positive input terminal and a second switching element connected to the negative input terminal are connected in series; a neutral leg in which a third switching element connected to the positive input terminal and a fourth switching element connected to the negative input terminal are connected in series; a second phase leg in which a fifth switching element connected to the positive input terminal and a sixth switching element connected to the negative input terminal are connected in series; having the first phase leg has a first phase connection point to which the first phase power line is connected, at a midpoint between the first switching element and the second switching element; the neutral leg has a neutral connection point to which the neutral power line is connected at a midpoint between the third switching element and the fourth switching element, the second phase leg has a second phase connection point to which the second phase power line is connected at a midpoint between the fifth switching element and the sixth switching element, The control unit is turning off the third switching element and the fourth switching element of the neutral leg; When the first switching element and the second switching element of the first phase leg and the fifth switching element and the sixth switching element of the second phase leg are PWM-controlled, The first short circuit and the second short circuit may be stopped, and the third short circuit may be operated.

[0030] According to this, when a single-phase three-wire inverter device is used as a single-phase two-wire inverter, by stopping the first short-circuit and the second short-circuit and operating the third short-circuit, when a short circuit is to be formed between the first phase power line and the second phase power line, only the third short-circuit is short-circuited, thereby making it possible to improve switching loss and switching noise.

[0031] In the present invention, The inverter unit is A positive input terminal connected to a positive terminal of a DC power supply and a negative input terminal connected to a negative terminal of the DC power supply are connected in parallel. a first phase leg in which a first switching element connected to the positive input terminal and a second switching element connected to the negative input terminal are connected in series; a third switching element connected to the positive input terminal; and a neutral leg in which a fourth switching element connected in series to the first switching element is connected; a second phase leg in which a fifth switching element connected to the positive input terminal and a sixth switching element connected to the negative input terminal are connected in series; having the first phase leg has a first phase connection point to which the first phase power line is connected, at a midpoint between the first switching element and the second switching element; the neutral leg has a neutral connection point to which the neutral power line is connected at a midpoint between the third switching element and the fourth switching element, the second phase leg has a second phase connection point to which the second phase power line is connected at a midpoint between the fifth switching element and the sixth switching element, The control unit is turning off the third switching element and the fourth switching element of the neutral leg; When the first switching element and the second switching element of the first phase leg and the fifth switching element and the sixth switching element of the second phase leg are PWM-controlled, The first short circuit, the second short circuit, and the third short circuit may be activated.

[0032] According to this, when a single-phase three-wire inverter device is used as a single-phase two-wire inverter, by operating the first short-circuit circuit, the second short-circuit circuit, and the third short-circuit circuit, when a short circuit is formed between the first phase power line and the second phase power line, the power line is short-circuited by the third short-circuit circuit and also by the first short-circuit circuit and the second short-circuit circuit, thereby improving the conduction loss of the switching elements.

[0033] The present invention also provides a method for producing a method for manufacturing a semiconductor device comprising the steps of: An inverter module that converts input DC power into single-phase three-wire AC power and outputs the converted power, a first phase output terminal, a second phase output terminal, and a neutral output terminal; an inverter unit that converts the DC power into the AC power; a first-phase power line connecting the inverter unit and the first-phase output terminal and through which the first-phase power of the AC power is supplied; a second-phase power line connecting the inverter unit and the second-phase output terminal and through which the second-phase power of the AC power is supplied; a neutral power line connecting the inverter unit and the neutral output terminal; a first short circuit connected between the first phase power line and the neutral power line and capable of short-circuiting the first phase power line and the neutral power line; a second short circuit connected between the second phase power line and the neutral power line and capable of short-circuiting the second phase power line and the neutral power line; Equipped with The inverter unit is A positive input terminal connected to a positive terminal of a DC power supply and a negative input terminal connected to a negative terminal of the DC power supply are connected in parallel. a first phase leg in which a first switching element connected to the positive input terminal and a second switching element connected to the negative input terminal are connected in series; a neutral leg in which a third switching element connected to the positive input terminal and a fourth switching element connected to the negative input terminal are connected in series; a second phase leg in which a fifth switching element connected to the positive input terminal and a sixth switching element connected to the negative input terminal are connected in series; having The first phase leg is provided at a midpoint between the first switching element and the second switching element. a first phase connection point to which the first phase power line is connected; the neutral leg has a neutral connection point to which the neutral power line is connected at a midpoint between the third switching element and the fourth switching element, The second phase leg has a second phase connection point, to which the second phase power line is connected, at a midpoint between the fifth switching element and the sixth switching element.

[0034] According to this, by configuring a single-phase three-wire three-arm inverter device using a single-phase three-wire inverter module, it is possible to suppress the variation in the characteristics of the inverter device, which allows for improved efficiency, improve heat dissipation, and make the inverter device easier to assemble. In addition, it is possible to reduce the size and cost compared to using two single-phase two-wire inverter modules.

[0035] The present invention also provides a method for producing a method for manufacturing a semiconductor device comprising the steps of: An inverter module that converts input DC power into single-phase three-wire AC power and outputs the converted power, a first phase output terminal, a second phase output terminal, and a neutral output terminal; an inverter unit that converts the DC power into the AC power; a first-phase power line connecting the inverter unit and the first-phase output terminal and through which the first-phase power of the AC power is supplied; a second-phase power line connecting the inverter unit and the second-phase output terminal and through which the second-phase power of the AC power is supplied; a neutral power line connecting the inverter unit and the neutral output terminal; a first short circuit connected between the first phase power line and the neutral power line and capable of short-circuiting the first phase power line and the neutral power line; a second short circuit connected between the second phase power line and the neutral power line and capable of short-circuiting the second phase power line and the neutral power line; Equipped with The inverter section is A positive input terminal connected to a positive terminal of a DC power supply and a negative input terminal connected to a negative terminal of the DC power supply are connected in parallel. a first phase leg in which a first switching element connected to the positive input terminal and a second switching element connected to the negative input terminal are connected in series; a neutral point circuit in which a first constant voltage source connected to the positive input terminal and a second constant voltage source connected to the negative input terminal are connected in series; a second phase leg in which a fifth switching element connected to the positive input terminal and a sixth switching element connected to the negative input terminal are connected in series; having the first phase leg has a first phase connection point to which the first phase power line is connected, at a midpoint between the first switching element and the second switching element; the neutral point circuit has a neutral connection point to which the neutral power line is connected at a midpoint between the first constant voltage source and the second constant voltage source, The second phase leg has a second phase connection point, to which the second phase power line is connected, at a midpoint between the fifth switching element and the sixth switching element.

[0036] According to this, by configuring a single-phase three-wire midpoint split type inverter device using a single-phase three-wire inverter module, it is possible to suppress the variation in the characteristics of the inverter device, which allows for improved efficiency, improves heat dissipation, and makes the inverter device easier to assemble. In addition, it is possible to reduce the size and cost compared to using two single-phase two-wire inverter modules. Effect of the Invention

[0037] According to the present invention, it is possible to improve the efficiency of a single-phase three-wire inverter device. [Brief description of the drawings]

[0038] [Figure 1] 1 is a diagram showing an outline of a circuit configuration of an inverter device according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a configuration of a HERIC circuit according to a first embodiment of the present invention. [Diagram 3] 4 is a timing chart of switching control of the inverter device according to the first embodiment of the present invention. [Figure 4] FIG. 2 is a diagram showing current paths in mode 1 of the inverter device according to the first embodiment of the present invention. [Diagram 5] FIG. 4 is a diagram showing current paths in mode 2 of the inverter device according to the first embodiment of the present invention. [Figure 6] FIG. 4 is a diagram showing current paths in mode 3 of the inverter device according to the first embodiment of the present invention. [Figure 7] FIG. 2 is a diagram illustrating switching control of the inverter device according to the first embodiment of the present invention. [Figure 8] FIG. 2 is a diagram illustrating switching control of the inverter device according to the first embodiment of the present invention. [Figure 9] FIG. 6 is a diagram showing an outline of a circuit configuration of an inverter device according to a second embodiment of the present invention. [Figure 10] 10 is a timing chart of switching control of an inverter device according to a third embodiment of the present invention. [Figure 11] FIG. 11 is a diagram showing current paths in mode 4 of an inverter device according to Example 3 of the present invention. [Figure 12] FIG. 11 is a diagram showing current paths in mode 5 of an inverter device according to Example 3 of the present invention. [Figure 13] FIG. 11 is a diagram showing a current path in mode 6 of an inverter device according to Example 3 of the present invention. [Figure 14] FIG. 11 is a diagram showing current paths in mode 7 of an inverter device according to Example 3 of the present invention. [Figure 15] FIG. 11 is a diagram showing an outline of a circuit configuration of an inverter device according to a fourth embodiment of the present invention. [Figure 16] FIG. 11 is a diagram showing an outline of a circuit configuration of an inverter device according to a fifth embodiment of the present invention. [Figure 17] FIG. 13 is a diagram showing an outline of a circuit configuration of an inverter module according to a sixth embodiment of the present invention. [Figure 18] FIG. 13 is a diagram showing an outline of a circuit configuration of an inverter device according to a ninth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] [Application example] Hereinafter, application examples of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of the circuit configuration of an inverter device 10 to which the present invention is applied.

[0040] The inverter device 10 generally comprises a single-phase three-wire inverter 11, a HERIC circuit 12 capable of short-circuiting between a U-phase power line Liu and a neutral wire Lio of the inverter 11, a HERIC circuit 13 capable of short-circuiting between a W-phase power line Liw and an O-phase neutral wire Lio of the inverter 11, and a control unit 14.

[0041] The single-phase three-wire inverter 11 is a three-arm inverter in which three legs, an O-phase midpoint leg Lgo, a U-phase leg Lgu, and a W-phase leg Lgw, are connected in parallel. The O-phase midpoint leg Lgo is The U-phase leg Lgu has switches SW3 and SW4 connected in series, the U-phase leg Lgu has switches SW1 and SW2 connected in series, and the W-phase leg Lgw has switches SW5 and SW6 connected in series.

[0042] A HERIC circuit 12 is connected between the U-phase power line Liu and the O-phase neutral line Lio, and a HERIC circuit 13 is connected between the O-phase neutral line Lio and the W-phase power line Liw. HERIC circuit 12 includes switches SWun and SWup, and HERIC circuit 13 includes switches SWwn and SWwp.

[0043] When converting the DC voltage output from the DC power supply Sd into a 50 Hz sine curve AC commercial voltage, in the first half of the cycle, the controller 14 controls the switches of the inverter 11 and the HERIC circuits 12 and 13 as shown in Fig. 3. Here, the controller 14 performs PWM control to control the output voltage by controlling the on / off duty ratio of the switches SW1 to Sw6 of the inverter 11.

[0044] In the first half cycle, the current path of the inverter device 10 repeats transitions among three modes in the order of mode 1, mode 2, and mode 3. In mode 1, the switch SW3 is off and the switch SW4 is on, and in mode 2, the switch SW3 is on and the switch SW4 is off. Then, in mode 3 following mode 2, when the U-phase power line Liu and the O-phase neutral line Lio are short-circuited by the HERIC circuit 12 and the O-phase neutral line Lio and the W-phase power line Liw are short-circuited by the HERIC circuit 13, both the switches SW3 and SW4 are off. In this manner, in the inverter device 10, while the switches SWun, SWup, SWwn, and SWwp of the HERIC circuits 12 and 13 are conductive, the upper and lower arms of the O-phase midpoint leg Lgo are controlled to stop operating.

[0045] In this way, according to the inverter device 10, it is possible to achieve high efficiency in a single-phase three-wire inverter device, and by stopping the operation of the O-phase midpoint leg Lgo during the period when the HERIC circuits 12 and 13 are short-circuited, when the input voltage is Vin, the potential of the midpoint Shp of the HERIC circuits 12 and 13 becomes Vin / 2, that is, the intermediate potential of the input voltage, thereby preventing the generation of noise.

[0046] Example 1 Hereinafter, the configuration of an inverter device 10 according to a first embodiment of the present invention will be described with reference to the drawings. However, the configurations of the device and system described in this embodiment should be appropriately modified depending on various conditions. In other words, it is not intended to limit the scope of the present invention to the following embodiment.

[0047] FIG. 1 is a circuit diagram showing a schematic configuration of an inverter device 10. As shown in FIG. The inverter device 10 is a power conversion device that is connected at input terminals Ip and In to the positive and negative terminals of a DC power source Sd, respectively, and converts DC power into AC power. The inverter device 10 supplies the converted AC power to loads RLi and Rlw connected between output terminals Ou and Oo, and between output terminals Ow and Oo, respectively, and can also be connected to a commercial power system. The output terminal Oo is grounded. Here, the input terminals Ip and In correspond to the positive side input terminal and the negative side input terminal, respectively, of the present invention. The output terminals Ou, Ow, and Ou correspond to the first phase output terminal, the second phase output terminal, and the neutral output terminal, respectively, of the present invention.

[0048] The inverter device 10 generally includes a single-phase three-wire inverter 11, a HERIC circuit 12 capable of short-circuiting a U-phase power line Liu and a neutral line Lio of the inverter 11, and a power supply circuit 13 for supplying a power to the inverter 11. The inverter 11 includes a HERIC circuit 13 capable of short-circuiting between the W-phase power line Liw and the neutral line Lio, and a control unit 14. Here, the inverter 11 and the control unit 14 correspond to the inverter unit and the control unit, respectively, of the present invention. Also, the HERIC circuit 12 and the HERIC circuit 13 correspond to the first short-circuit and the second short-circuit, respectively, of the present invention.

[0049] (Inverter) The single-phase three-wire inverter 11 is a three-arm inverter in which a leg consisting of two switches connected in series is connected in parallel to a DC power source Sd. That is, the inverter 11 is configured with three legs, an O-phase midpoint leg Lgo, a U-phase leg Lgu, and a W-phase leg Lgw, connected in parallel between a positive input line Lip and a negative input line Lin, in that order from the input terminals Ip and In side. Here, the switches are made of n-channel enhancement type MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors) which are semiconductor switching elements. The semiconductor switching element can be an IGBT (Insulated Gate Bipolar Transistor), but in this case, a free-wheeling diode connected in reverse parallel to the IGBT is used. A switch is formed by combining the O-phase midpoint leg Lgo, the U-phase leg Lgu, and the W-phase leg Lgw here correspond to the neutral leg, the first phase leg, and the second phase leg of the present invention, respectively.

[0050] The U-phase leg Lgu is composed of a switch SW1 and a switch SW2, the drain terminal of the switch SW1 is connected to the positive input line Lip, the source terminal of the switch SW1 is connected to the drain terminal of the switch SW2, and the source terminal of the switch SW2 is connected to the negative input line Lin. The O-phase midpoint leg Lgo is composed of a switch SW3 and a switch SW4, the drain terminal of the switch SW3 is connected to the positive input line Lip, the source terminal of the switch SW3 is connected to the drain terminal of the switch SW4, and the source terminal of the switch SW4 is connected to the negative input line Lin. The W-phase leg Lgw is composed of a switch SW5 and a switch SW6, the drain terminal of the switch SW5 is connected to the positive input line Lip, the source terminal of the switch SW5 is connected to the drain terminal of the switch SW6, and the source terminal of the switch SW6 is connected to the negative input line Lin. Here, the switches SW1 and SW2 correspond to the first and second switching elements of the present invention. The switches SW3 and SW4 correspond to the third and fourth switching elements of the present invention. Moreover, the switches SW5 and SW6 correspond to the fifth switching element and the sixth switching element of the present invention.

[0051] An O-phase neutral wire Lio is drawn from the midpoint of the O-phase midpoint leg Lgo, i.e., the midpoint Cpo between the source terminal of the switch SW3 and the drain terminal of the switch SW4. A U-phase power line Liu is drawn from the midpoint of the U-phase leg Lgu, i.e., the midpoint Cpu between the source terminal of the switch SW1 and the drain terminal of the switch SW2. A W-phase power line Liw is drawn from the midpoint of the W-phase leg Lgw, i.e., the midpoint Cpw between the source terminal of the switch SW5 and the drain terminal of the switch SW6. Here, the midpoint Cpo and the O-phase neutral wire Lio correspond to the neutral connection point and neutral power line of the present invention, respectively. Also, the midpoint Cpu and the U-phase power line Liu correspond to the first phase connection point and first phase power line of the present invention, respectively. Also, the midpoint Cpw and the W-phase power line Liw correspond to the second phase connection point and second phase power line of the present invention, respectively.

[0052] HERIC circuit 12 is connected between U-phase power line Liu and O-phase neutral line Lio, and HERIC circuit 13 is connected between O-phase neutral line Lio and W-phase power line Liw. On the output terminal Ou, Oo, and Ow sides of HERIC circuit 12 and HERIC circuit 13, reactor Lu, reactor Lo, and reactor Lw are connected in series to the U-phase power line Liu, the O-phase neutral line Lio, and the W-phase power line Liw, respectively.

[0053] The output end Ou side of the reactor Lu of the U-phase power line Liu and the reactor Lio of the O-phase neutral line A capacitor Cu is connected between the output terminal Oo side of the O-phase neutral conductor Lio and the W-phase power line Liw. A capacitor Cw is connected between the output terminal Lo side of the O-phase neutral conductor Lio and the W-phase power line Liw. That is, the capacitor Cu and the HERIC circuit 12 are connected in parallel between the U-phase power line Liu and the O-phase neutral conductor Lio, in this order from the output terminal Ou and the output terminal Oo side. Also, the capacitor Cw and the HERIC circuit 13 are connected in parallel between the O-phase neutral conductor Lio and the W-phase power line Liw, in this order from the output terminal Oo and the output terminal Ow side.

[0054] A load RLu is connected between the output terminal Ou of the U-phase power line Liu and the output terminal Oo of the O-phase neutral line Lio, and a load RLw is connected between the output terminal Ou of the O-phase power line Liu and the output terminal Ow of the W-phase power line Liw.

[0055] (HERIC circuit) The HERIC circuit 12 includes switches SWun and SWup, which are made up of n-channel enhancement type MOSFETs. Although not shown in FIG. 1, the HERIC circuit 12 has a gate drive circuit that drives the gates of the switches SWun and SWup. The gate drive circuit controls the on / off of the switches SWun and SWup based on instructions from a control unit 14 that controls the operation of the inverter device 10.

[0056] The source terminal of switch SWup of HERIC circuit 12 is connected to the U-phase power line Liu, the drain terminal of switch SWup is connected to the drain terminal of switch SWun, and the source terminal of switch SWun is connected to the neutral line Lio. Here, switch SWup and switch SWun correspond to the first short-circuit switching element and the second short-circuit switching element of the present invention, respectively.

[0057] The HERIC circuit 13 includes switches SWwn and SWwp each formed of an n-channel enhancement type MOSFET. Although omitted in FIG. 1, the HERIC circuit 13 has a gate drive circuit for driving the gates of the switches SWwn and SWwp. The gate drive circuit controls the on / off of the switches SWwn and SWwp based on instructions from a control unit 14 that controls the operation of the inverter device 10.

[0058] The source terminal of switch SWwn of HERIC circuit 13 is connected to the W-phase power line Liw, the drain terminal of switch SWwn is connected to the drain terminal of switch SWwp, and the source terminal of switch SWwp is connected to the neutral line Lio. Here, switches SWwp and SWwn correspond to the third and fourth short-circuit switching elements of the present invention.

[0059] The specific configuration of the HERIC circuit is not limited to HERIC circuit 12 and HERIC circuit 13. 2(A) to (D) show specific examples of the HERIC circuit.

[0060] 2(A) is a diagram showing the basic configuration of the HERIC circuit Hr1. A switch S1 and a diode D1 connected in series, and a diode D2 and a switch S2 connected in series are connected in parallel between the power line Li1 and the power line Li2. The cathode and anode terminals of the diode D1 are connected to the power line Li1 side and the power line Li2 side, respectively. The cathode and anode terminals of the diode D2 are connected to the power line Li2 side and the power line Li1 side, respectively. As the switches S1 and S2, semiconductor switching elements such as IGBTs and MOSFETs can be used.

[0061] Here, when the power line Li1 is at a higher potential than the power line Li2, no current flows even if the switch S1 is closed because the diode D1 is connected in the reverse direction. When power line Li1 and power line Li2 become equipotential, diode D1 turns on, commutating the load current and shorting power lines Li1 and Li2.

[0062] 2B is a diagram showing the basic configuration of the HERIC circuit Hr2. The HERIC circuit Hr2 has the same configuration as the HERIC circuit Hr1, except that the midpoint between the switch S1 and the diode D1 and the midpoint between the switch S2 and the diode D2 are connected by a connection line Sc1.

[0063] Here, when power line Li1 is at a higher potential than power line Li2, no current flows even if switch S1 is closed because diode D1 is connected in the reverse direction. When power line Li2 has the same potential as power line Li1, diode D1 turns on, commutating the load current and shorting power lines Li1 and Li2.

[0064] In the HERIC circuit Hr3 shown in FIG. 2(C), switches SW31 and SW32, each composed of an n-channel enhancement type MOSFET, are connected in series between the power lines Li1 and Li2. The drain terminal of switch SW31 in the HERIC circuit Hr3 is connected to the power line Li1, the source terminal of switch SW31 is connected to the source terminal of switch SW32, and the drain terminal of switch SW32 is connected to the power line Li2. This HERIC circuit Hr3 has the same configuration as the HERIC circuit 12 shown in FIG. 1. This HERIC circuit Hr3 has the same functions as the HERIC circuit Hr2 shown in FIG. 2(B).

[0065] In the HERIC circuit Hr4 shown in Fig. 2(D), switches SW41 and SW42, each composed of an n-channel enhancement type MOSFET, are connected in series between the power lines Li1 and Li2. The source terminal of the switch SW41 in the HERIC circuit Hr4 is connected to the power line Li1, the drain terminal of the switch SW41 is connected to the drain terminal of the switch SW42, and the source terminal of the switch SW42 is connected to the power line Li2. This HERIC circuit Hr4 has the same configuration as the HERIC circuit 13 shown in Fig. 1. This HERIC circuit Hr4 has the same functions as the HERIC circuit Hr3 shown in Fig. 2(C).

[0066] (PWM control) The switching control of the inverter 11 and the HERIC circuits 12 and 13 for converting input DC power into AC power in the inverter device 10 will be described below.

[0067] The control unit 14 performs switching control of the inverter 11 and the HERIC circuits 12 and 13 based on a command value related to an AC voltage waveform to be output (for example, a sine curve of 50 Hz). Here, the control unit 14 performs PWM control to control the output voltage by controlling the on / off duty ratio of the switches SW1 to SW6 of the inverter 11.

[0068] Fig. 3 shows a part of a timing chart of control signals for each switch of the inverter 11 and the HERIC circuits 12 and 13 in the power conversion process by the inverter device 10. Fig. 3 shows control signals for each switch in the first half cycle when outputting an AC voltage that draws a sine curve with a frequency of 50 Hz, the same as commercial power.

[0069] PWM control by unipolar modulation is performed on the inverter 11. On / off of each switch is controlled according to a duty ratio determined by the PWM control. In the first half cycle, a voltage is output to the output terminal Ou of the U-phase power line Liu and the output terminal Oo of the O-phase neutral line Lio, and the voltage applied to the load RLiu is positive or zero on the output terminal Ou side with respect to the output terminal Oo side, and is output to the output terminal Oo of the O-phase neutral line Lio and the output terminal Ow of the W-phase power line Liw, and the voltage applied to the load Rlw is positive or zero on the output terminal Oo side with respect to the output terminal Ow side. In the second half cycle, a voltage is output to the output terminal Ou of the U-phase power line Liu and the output terminal Oo of the O-phase neutral line Lio, and the voltage applied to the load Rlw is positive or zero on the output terminal Oo side with respect to the output terminal Ow side. The voltage outputted and applied to the load RLiu is negative or zero on the output terminal Ou side relative to the output terminal Oo side, and the voltage outputted to the output terminal Oo of the O-phase neutral wire Lio and the output terminal Ow of the W-phase power line Liw is negative or zero on the output terminal Oo side relative to the output terminal Ow side.

[0070] In the first half cycle, the current path of the inverter device 10 repeats transitions among three modes in the order of mode 1, mode 2, and mode 3. Here, mode 1, mode 2, and mode 3 correspond to the first mode, second mode, and third mode, respectively, of the present invention.

[0071] 4 shows the current paths of the inverter device 10 in mode 1. The path of the current Iu flowing through the load RLu is shown by a solid line, the path of the current Iw flowing through the load RLw is shown by a dashed line, and the dashed line shows other current paths. Here, the switch SW1 is on, the switch SW2 is off, the switch SW3 is off, the switch SW4 is on, the switch SW5 is off, the switch SW6 is on, the switch SWup is on, the switch SWun is off, the switch SWwp is on, and the switch SWun is off. At this time, the current input from the positive terminal of the DC power supply Sd through the input terminal Ip to the positive input line Lip passes through the switch SW1, the U-phase power line Liu, the reactor Lu, the load RLu, the reactor Lo, the O-phase neutral line Lio, the switch SW4, and the negative input line Lin, and returns from the input terminal In to the negative terminal of the DC power supply Sd. On the other hand, the current flowing through the load RLw flows from the reactor Lw to the W-phase power line Liw, the switch SW6, the negative input line Lin, the switch SW4, the O-phase neutral line Lio, the reactor Lo, and the load RLw. There is also a current path that flows from the load RLw, the reactor Lw, the W-phase power line Liw, the switch SW6, the negative input line Lin, and the input terminal In.

[0072] 5 shows the current paths of the inverter device 10 in mode 2. As in FIG. 4, the path of the current Iu flowing through the load RLu is shown by a solid line, the path of the current Iw flowing through the load RLw is shown by a dashed line, and the two-dot chain line shows other current paths. Here, the switch SW1 is on, the switch SW2 is off, the switch SW3 is on, the switch SW4 is off, the switch SW5 is off, the switch SW6 is on, the switch SWup is on, the switch SWun is off, the switch SWwp is on, and the switch SWun is off. At this time, the current input from the positive terminal of the DC power supply Sd through the input terminal Ip to the positive input line Lip passes through the switch SW3, the O-phase neutral line Lio, the reactor Lo, the load RLw, the reactor Lw, the W-phase power line Liw, the switch SW6, and the negative input line Lin, and returns from the input terminal In to the negative terminal of the DC power supply Sd. On the other hand, the current flowing through the load RLiu passes through the positive input line Lip, switch SW1, U-phase power line Liu, reactor Lu, load Rlu, O-phase neutral line Lio, reactor Lo, switch SW3, and the positive input line Lip. There is also a current path that flows from the positive input line Lip to the switch SW1, U-phase power line Liu, reactor Lu, load RLiu, and load Rlw.

[0073] 6 shows a current path of the inverter device 10 in mode 3. Here, the switches SW1 to SW6 are all off, the switch SWup is on, the switch SWun is off, the switch SWwp is on, and the switch SWun is off. At this time, the current flowing through the load LRu passes through the load RLu, the O-phase neutral line Lio, the reactor Lo, the switch SWup, the switch SWun, the U-phase power line Liu, the reactor Lu, and the load RLu, and the HERIC circuit 12 is short-circuited. Although the switch SWun of the HERIC circuit 12 is off, the parasitic diode of the MOSFET, which is a switching element, is conductive, and a current flows from the O-phase neutral line Lio to the U-phase power line Liu. On the other hand, the current flowing through the load RLw passes through the load RLw, the W-phase power line Liw, the reactor Lw, the switch SWwn, the switch SWwp, the O-phase neutral line Lio, the reactor Lio, and the load RLw, and the HERIC circuit 13 is short-circuited. Although switch SWwn of HERIC circuit 13 is off, the parasitic diode of the MOSFET, which is a switching element, is conductive, and current flows from W-phase power line Liw to neutral line Lio.

[0074] The control of each switch in the latter half cycle of the commercial frequency will be briefly described. In this case, the control repeats transition in the order of mode 1-2, mode 2-2, and mode 3-2. Mode 1-2 is a mode in which the on / off states of the switch SW1 and the switch SW5 in mode 1 are interchanged, the on / off states of the switch SW2 and the switch SW6 are interchanged, the switch SWun is turned on, and the switch SWwn is turned on. Mode 2-2 is a mode in which the on / off states of the switch SW1 and the switch SW5 in mode 2 are interchanged, the on / off states of the switch SW2 and the switch SW6 are interchanged, the switch SWun is turned on, and the switch SWwn is turned on. And mode 3-2 is a mode in which the switch SW1, the switch SW2, the switch SW3, the switch SW4, the switch SW5, and the switch SW6 are all turned off, the switch SWun is turned on, and the switch SWwn is turned on. Here, mode 1-2, mode 2-2, and mode 3-2 correspond to the 1-2 mode, the 2-2 mode, and the 3-2 mode of the present invention, respectively. Here, the first and second half cycles of the commercial frequency correspond to one and the other half cycles of the frequency of the AC power to be output, respectively, of the present invention.

[0075] In this way, a single-phase three-wire inverter device 10 using a HERIC circuit can be realized, and high efficiency can be achieved. In such an inverter device 10, a load current can also be passed through the O-phase neutral wire Lio, and the U-phase current Iu flowing through the U-phase power line Liu and the W-phase current Iw flowing through the W-phase power line Liw do not need to be the same. Therefore, when the U-phase load RLu and the W-phase load RLw are not balanced, such as during an independent operation, the inverter device 10 can be driven independently between the U-phase power line Liu and the O-phase neutral wire Lio, and between the W-phase power line Liw and the O-phase neutral wire Lio. As described above, in the inverter device 10, in mode 3 in which the HERIC circuits 12 and 13 are shorted, the switches SW3 and SW4 of the upper and lower arms of the O-phase midpoint leg Lgo are turned off and stop operating. This is because, as shown in Fig. 7, when the O-phase midpoint leg Lgo is operated during the period in which the HERIC circuits 12 and 13 are shorted, there are moments when the midpoint Shp of the HERIC circuits 12 and 13 becomes equal to the potential of the positive input line Lip at point Pp, and moments when it becomes equal to the potential of the negative input line Lin at point Np, as shown in Fig. 8. For this reason, the potential of the midpoint Shp of the HERIC circuits 12 and 13 fluctuates drastically, causing noise. Therefore, in mode 3, which is the period during which the HERIC circuits 12 and 13 are short-circuited, the operation of the O-phase midpoint leg Lgo is stopped and the switches SW3 and SW4 are turned off, so that when the input voltage is Vin, the potential of the midpoint Shp of the HERIC circuits 12 and 13 becomes Vin / 2, that is, the intermediate potential of the input voltage, thereby making it possible to avoid the generation of noise.

[0076] Example 2 Hereinafter, a description will be given of the inverter device 20 according to the second embodiment. Fig. 9 is a circuit diagram showing a schematic configuration of the inverter device 20. Configurations common to the first embodiment will be given the same reference numerals and detailed description will be omitted. The inverter device 20 generally includes a single-phase three-wire inverter 21, a midpoint control auxiliary circuit 22, a HERIC circuit 12 capable of short-circuiting between a U-phase power line Liu and a neutral wire Lio of the inverter 21, a HERIC circuit 13 capable of short-circuiting between a W-phase power line Liw and a neutral wire Lio of the inverter 11, and a control unit 24.

[0077] The inverter 21 is a single-phase three-wire inverter similar to the inverter 11 according to the first embodiment, but a capacitor C1 and a capacitor C2 are connected in parallel to the input terminals Ip and In of the U-phase leg Lgu and the W-phase leg Lgw that constitute a full bridge. The capacitors C1 and C2 are connected in series between the positive input line Lip and the negative input line Lin. A midpoint Cpo of the capacitors C1 and C2 is connected to the O-phase neutral line. Here, the capacitors C1 and C2 correspond to the first constant voltage source and the second constant voltage source of the present invention.

[0078] A neutral point control auxiliary circuit 22 is provided on the input terminals Ip and In of the capacitors C1 and C2. The neutral point control auxiliary circuit 22 is composed of two switches SW3 and SW4 constituting the O-phase neutral leg Lgo according to the first embodiment, and a reactance Lo connected in series to the O-phase neutral conductor Lio drawn from the midpoint Cps of the switches SW3 and SW4. Here, the neutral point control auxiliary circuit 22 and the midpoint Cps correspond to the neutral point circuit and the second neutral connection point of the present invention, respectively.

[0079] Capacitors C1 and C2 that constitute the inverter 11 operate as constant voltage sources, and any element, circuit, or device that operates as a constant voltage source, such as a capacitor, a battery, or a constant voltage circuit, can be used in place of capacitors C1 and C2.

[0080] The midpoint control auxiliary circuit 22 has a common configuration with the O-phase midpoint leg Lgo in Example 1, and appears to be a three-arm inverter, but it is an auxiliary circuit that balances the midpoints of the capacitors C1 and C2, and a configuration without such a midpoint control auxiliary circuit 22 is also possible.

[0081] The operation of the inverter device 20 is similar to that of the inverter device 10 according to the first embodiment, and therefore a detailed description thereof will be omitted.

[0082] Example 3 Hereinafter, a description will be given of an inverter device 30 according to the third embodiment. Since the configuration of the inverter device 30 is the same as that of the inverter device 10 according to the first embodiment, the same reference numerals are used and detailed description will be omitted.

[0083] 10 shows a part of a timing chart of control signals for each switch of the inverter 11 and the HERIC circuits 12 and 13 for converting input DC power into AC power in the inverter device 30. Here too, the control signals for each switch in the first half cycle are shown when outputting an AC voltage that draws a sine curve with a frequency of 50 Hz, the same as commercial power.

[0084] In the inverter device 30, the inverter 11 is also subjected to PWM control by unipolar modulation. On / off of each switch is controlled according to a duty ratio determined by the PWM control. In the first half cycle, a voltage is output to the output terminal Ou of the U-phase power line Liu and the output terminal Oo of the O-phase neutral line Lio, and the voltage applied to the load RLiu is positive or zero on the output terminal Ou side with respect to the output terminal Oo side, and a voltage is output to the output terminal Oo of the O-phase neutral line Lio and the output terminal Ow of the W-phase power line Liw, and the voltage applied to the load Rlw is positive or zero on the output terminal Oo side with respect to the output terminal Ow side. In the second half cycle, the voltage applied to the load RLiu is negative or zero on the output terminal Ou side relative to the output terminal Oo side, and the voltage applied to the load RLiu is negative or zero on the output terminal Ou side relative to the output terminal Oo side, and the voltage applied to the load Rlw is negative or zero on the output terminal Oo side relative to the output terminal Ow side.

[0085] In the first half cycle, the current path of the inverter device 30 repeats four mode transitions in the order of mode 4, mode 5, mode 6, and mode 7. Here, mode 4, mode 5, mode 6, and mode 7 correspond to the fourth mode, the fifth mode, the sixth mode, and the seventh mode of the present invention. Each corresponds to the other.

[0086] 11 shows the current path of the inverter device 30 in mode 4. Here, too, the path of the current Iu flowing through the load RLu is shown by a solid line, the path of the current Iw flowing through the load RLw is shown by a dashed line, and the dashed line shows other current paths. The current path of the inverter device 30 in mode 4 is the same as the current path of the inverter device 10 in the mode 1 according to the first embodiment. That is, the switch SW1 is on, the switch SW2 is off, the switch SW3 is off, the switch SW4 is on, the switch SW5 is off, the switch SW6 is on, the switch SWup is on, the switch SWun is off, the switch SWwp is on, and the switch SWun is off. Then, the current input from the positive terminal of the DC power supply Sd through the input terminal Ip to the positive input line Lip passes through the switch SW1, the U-phase power line Liu, the reactor Lu, the load RLu, the reactor Lo, the O-phase neutral line Lio, the switch SW4, and the negative input line Lin, and returns from the input terminal In to the negative terminal of the DC power supply Sd. On the other hand, the current flowing through the load RLw flows from the reactor Lw to the W-phase power line Liw, the switch SW6, the negative input line Lin, the switch SW4, the O-phase neutral line Lio, the reactor Lo, and the load RLw. There is also a current path that flows from the load RLw, the reactor Lw, the W-phase power line Liw, the switch SW6, the negative input line Lin, and the input terminal In.

[0087] 12 shows the current path of the inverter device 30 in mode 5. Here, the switch SW1 is on, the switch SW2 is off, the switch SW3 is on, the switch SW4 is off, the switch SW5 is off, the switch SW6 is on, the switch SWup is on, the switch SWun is off, the switch SWwp is on, and the switch SWun is off. At this time, the current input from the positive terminal of the DC power supply Sd through the input terminal Ip to the positive input line Lip passes through the switch SW3, the O-phase neutral line Lio, the reactor Lo, the load RLw, the reactor Lw, the W-phase power line Liw, the switch SW6, and the negative input line Lin, and returns from the input terminal In to the negative terminal of the DC power supply Sd. On the other hand, the current flowing through the load RLu flows through the path of the reactor Lu, the load Rlu, the O-phase neutral line Lio, the reactor Lo, the switch SWup, the switch SWun, and the U-phase power line Liu. There is also a current path that flows from the positive input line Lip, the switch SW1, the U-phase power line Liu, the reactor Lu, the load Rlu, the O-phase neutral line Lio, the switch SW3, and back to the positive input line Lip.

[0088] 13 shows the current paths of the inverter device 30 in mode 6. The two-dot chain lines show other current paths. Here, the switch SW1 is off, the switch SW2 is on, the switch SW3 is on, the switch SW4 is off, the switch SW5 is on, the switch SW6 is off, the switch SWup is on, the switch SWun is off, the switch SWwp is on, and the switch SWun is off. The current flowing through the load Rlu flows through the path of the U-phase power line Liu, the reactor Lu, the load Rlu, the O-phase neutral line Lio, the reactor Lo, the switch SWup, the switch SWun, and the U-phase power line Liu. The current flowing through the load RLw flows through the path of the switch SWwn, the switch SWwp, the O-phase neutral line Lio, the reactor Lo, the load RLw, the W-phase power line Liw, the reactor Lw, and the switch SWwn. There is also a current path that flows from the positive input line Lip, switch SW5, W-phase power line Liw, reactor Lw, load RLw, O-phase neutral line Lio, reactor Lo, switch SW3, and the positive input line Lip. There is also a current path that flows from the reactor Lo, O-phase power line Lio, switch SWup, switch SWun, U-phase power line Liu, reactor Lu, load Rlu, and O-phase power line Lio.

[0089] 14 shows the current path of the inverter device 30 in mode 7. Here, the switch SW1 is off, the switch SW2 is on, the switch SW3 is off, the switch SW4 is on, the switch SW5 is on, the switch SW6 is off, the switch SWup is on, the switch SWun is off, the switch SWwp is on, and the switch SWun is off. The current flowing through u flows through the U-phase power line Liu, reactor Lu, load Rlu, O-phase neutral line Lio, reactor Lo, switch SWup, switch SWun, and U-phase power line Liu. There is also a current path that flows through switch SW4, O-phase power line Lio, reactor Lo, load Rlu, U-phase power line Liu, reactor Lu, switch SW2, negative input line Lin, and switch SW2. On the other hand, the current flowing through load RLw flows through the switch SWwn, switch SWwp, O-phase neutral line Lio, reactor Lo, load RLw, W-phase power line Liw, reactor Lw, and switch SWwn.

[0090] In the PWM control in the inverter device 30, as described above, transitions are repeated in the order of mode 4, mode 5, mode 6, and mode 7 in the first half cycle. As described for the inverter device 10 in the unipolar drive, if a stop period is provided in the control of the O-phase midpoint leg Lgo, the modulation rate decreases. However, by performing control like the inverter device 30 according to the present embodiment and operating the O-phase midpoint leg Lgo rather than stopping it in modes 6 and 7 in which the HERIC circuits 12 and 13 are short-circuited, it is possible to avoid a decrease in the modulation rate.

[0091] The control of each switch in the latter half cycle of the commercial frequency will be briefly described. In this case, the control repeats transition in the order of mode 4-2, mode 5-2, mode 6-2, and mode 7-2. Mode 4-2, mode 5-2, mode 6-2, and mode 7-2 are modes in which the on / off states of the switches SW1 and SW5 are switched, the on / off states of the switches SW3 and SW4 are switched, the on / off states of the switches SW2 and SW6 are switched, the switches SWun are turned on, and the switches SWwn are turned on in mode 4, mode 5, mode 6, and mode 7, respectively. Here, mode 4-2, mode 5-2, mode 6-2, and mode 7-2 correspond to mode 4-2, mode 5-2, mode 6-2, and mode 7-2 of the present invention. Also, here, the first half cycle and the second half cycle of the commercial frequency correspond to one half cycle and the other half cycle of the frequency of the AC power to be output, respectively, of the present invention.

[0092] In the PWM control in the inverter device 30, as described above, transitions are repeated in the order of mode 4-2, mode 5-2, mode 6-2, and mode 7-2 in the latter half of the cycle. As described for the inverter device 10 in the unipolar drive, if a stop period is provided in the control of the O-phase midpoint leg Lgo, the modulation rate decreases, but by performing control like the inverter device 30 according to the present embodiment and operating the O-phase midpoint leg Lgo instead of stopping it in modes 6-2 and 7-2 in which the HERIC circuits 12 and 13 are short-circuited, it is possible to avoid a decrease in the modulation rate.

[0093] Example 4 An inverter device 40 according to the fourth embodiment will be described below. Fig. 15 shows the circuit configuration of the inverter device 40. The same components as those in the first embodiment are designated by the same reference numerals and detailed description thereof will be omitted. The circuit configuration of the inverter device 40 is the same as that of the inverter device 10, but as shown in Fig. 15, the inverter device 40 uses two single-phase two-wire HERIC modules.

[0094] In FIG. 15, a circuit including the O-phase midpoint leg Lgo, the U-phase leg Lgu, and the HERIC circuit 12, which are surrounded by a dashed line, is configured by a single-phase two-wire HERIC module Md1. Also, in FIG. 15, a circuit including the W-phase leg Lgw, and the HERIC circuit 13, which are surrounded by a dashed line, is configured by a single-phase two-wire HERIC module Md2. For this HERIC module Md2, only one of the two legs that configure a full bridge is used. It is also possible to use one leg of the HERIC module Md2 as the O-phase midpoint leg Lgo, and to configure two O-phase midpoint legs Lgo in parallel. Here, the HERIC modules Md1 and H The ERIC module Md2 corresponds to the first single-phase two-wire inverter module and the second single-phase two-wire inverter module of the present invention, respectively. In this way, by configuring the inverter device 40 using two single-phase two-wire HERIC modules Md1 and Md2, it is possible to suppress variation in the characteristics of the inverter device 40, improve heat dissipation, and make assembly easier.

[0095] Example 5 An inverter device 50 according to the fifth embodiment will be described below. Fig. 16 shows the circuit configuration of the inverter device 50. The same components as those in the second embodiment are designated by the same reference numerals and detailed description thereof will be omitted. The circuit configuration of the inverter device 50 is the same as that of the inverter device 20, but as shown in Fig. 16, the inverter device 50 uses two single-phase two-wire HERIC modules.

[0096] In Fig. 16, a circuit including the midpoint control auxiliary circuit 22, the U-phase leg Lgu, and the HERIC circuit 12 surrounded by a dashed line is configured by a single-phase two-wire HERIC module Md3. Also, in Fig. 16, a circuit including the W-phase leg Lgw and the HERIC circuit 13 surrounded by a dashed line is configured by a single-phase two-wire HERIC module Md4. For this HERIC module Md4, only one of the two legs constituting a full bridge is used. Here, the HERIC module Md3 and the HERIC module Md4 correspond to the third single-phase two-wire inverter module and the fourth single-phase two-wire inverter module of the present invention, respectively. Also, the midpoint control auxiliary circuit 22 corresponds to the third leg of the present invention. In this way, by configuring the inverter device 50 using two single-phase two-wire HERIC modules Md1 and Md2, it is possible to suppress variation in the characteristics of the inverter device 50, improve heat dissipation, and make assembly easier.

[0097] Example 6 Hereinafter, a single-phase three-wire inverter module 60 according to the sixth embodiment will be described. Fig. 17 shows a circuit configuration of the module 60. The module 60 is a modularized version of the inverter device 10 according to the first embodiment.

[0098] Module 60 has input terminals DC+ and DC-, and output terminals OUT U, OUT O, and OUT W. Module 60 generally includes a single-phase three-wire inverter 61, a HERIC circuit 62 capable of short-circuiting between a U-phase power line Liu and a neutral wire Lio of inverter 61, and a HERIC circuit 63 capable of short-circuiting between a W-phase power line Liw and a neutral wire Lio of inverter 61.

[0099] The single-phase three-wire inverter 61 is a three-arm inverter in which a leg consisting of two switches connected in series is connected in parallel to the input terminals DC+ and DC-. That is, the inverter 61 is configured with three legs, an O-phase midpoint leg MLgo, a U-phase leg MLgu, and a W-phase leg MLgw, connected in parallel between the positive input line Lip and the negative input line Lin, in that order from the input terminals DC+ and DC-. Here, the switches are configured of n-channel enhancement type MOSFETs, which are semiconductor switching elements. An IGBT can also be used as the semiconductor switching element, but in this case, the switch is configured by combining the IGBT with a free wheel diode connected in inverse parallel.

[0100] The U-phase leg MLgu is composed of a switch M1 and a switch M2. The drain terminal of the switch M1 is connected to the positive input line Lip, the source terminal side of the switch M1 is connected to the drain terminal of the switch M2, and the gate terminal connection line G1 and the source terminal connection line S1 of the switch M1 are drawn out. The source terminal side of the switch M2 is connected to the negative input line Lin, and the gate terminal connection line G2 and the source terminal connection line S2 of the switch M2 are drawn out. The O-phase midpoint leg MLgo is composed of a switch M3 and a switch M4. The drain terminal of the switch M3 is connected to the positive input line Lip, the source terminal side of the switch M3 is connected to the drain terminal of the switch M4, and the gate terminal connection line G3 and the source terminal connection line S3 of the switch M3 are drawn out. The source terminal side of the switch M4 is connected to the negative input line Lin, and the gate terminal connection line G4 and the source terminal connection line S4 of the switch M4 are drawn out. The W-phase leg MLgw is composed of a switch M5 and a switch M6. The drain terminal of the switch M5 is connected to the positive input line Lip, the source terminal side of the switch M5 is connected to the drain terminal of the switch M6, and the gate terminal connection line G5 and the source terminal connection line S5 of the switch M5 are drawn out. The source terminal side of the switch M6 is connected to the negative input line Lin, and the gate terminal connection line G6 and the source terminal connection line S6 of the switch M6 are drawn out.

[0101] An O-phase neutral wire Lio is drawn from the midpoint of the O-phase midpoint leg Lgo, i.e., the midpoint between the source terminal of switch SW3 and the drain terminal of switch SW4. A U-phase power line Liu is drawn from the midpoint of the U-phase leg Lgu, i.e., the midpoint between the source terminal of switch SW1 and the drain terminal of switch SW2. A W-phase power line Liw is drawn from the midpoint of the W-phase leg Lgw, i.e., the midpoint between the source terminal of SW5 and the drain terminal of switch SW6.

[0102] A HERIC circuit 12 is connected between the U-phase power line Liu and the O-phase neutral line Lio, and a HERIC circuit 13 is connected between the O-phase neutral line Lio and the W-phase power line Liw.

[0103] HERIC circuit 62 includes switches USH and USL each composed of an n-channel enhancement type MOSFET. The source terminal of switch USL in HERIC circuit 12 is connected to U-phase power line Liu, the drain terminal of switch USL is connected to the drain terminal of switch USH, and the source terminal of switch USH is connected to neutral line Lio. In addition, a gate terminal connection line GUSH and a source terminal connection line SUSH of switch USH are drawn out, and a gate terminal connection line GUSL and a source terminal connection line SUSL of switch USL are drawn out.

[0104] HERIC circuit 63 includes switches WSH and WSL each composed of an n-channel enhancement type MOSFET. The source terminal of switch WSH of HERIC circuit 63 is connected to W-phase power line Liw, the drain terminal of switch WSH is connected to the drain terminal of switch WSL, and the source terminal of switch WSL is connected to neutral line Lio. In addition, a gate terminal connection line GWSH and a source terminal connection line SWSH of switch WSH are drawn out, and a gate terminal connection line GWSL and a source terminal connection line SWSL of switch WSL are drawn out.

[0105] In this way, by using the single-phase three-wire HERIC module 60, it is possible to suppress the variation in the characteristics of the inverter device, improve heat dissipation, and facilitate assembly. In addition, it is possible to reduce the size and cost compared to using two single-phase two-wire HERIC modules.

[0106] Example 7 Hereinafter, a description will be given of an inverter device 70 according to the seventh embodiment. The configuration of the inverter device 70 is the same as that of the inverter device 10 according to the first embodiment, and therefore a detailed description of the circuit configuration will be omitted.

[0107] In the inverter device 70, when the inverter device 70 is operated as a single-phase two-wire inverter device during grid interconnection or the like, the O-phase midpoint leg Lgo is stopped, and the switch SW3 and In this case, the operation of the U-phase leg Lgu, the W-phase leg Lgw, the HERIC circuit 12, and the HERIC circuit 13 is controlled by the same PWM pattern as that of a normal single-phase two-wire inverter device. Here, the HERIC circuits 12 and 13 perform the same operation.

[0108] A relay may be provided on the O-phase neutral wire Lio between the midpoint of HERIC circuit 12 and HERIC circuit 13 and output terminal Oo, and when inverter device 70 is operated as a single-phase two-wire inverter device during system interconnection or the like, this relay may be opened to interrupt the circuit.

[0109] In this way, efficient power conversion is possible even when the inverter device 70 is operated as a single-phase two-wire inverter device during grid interconnection or the like.

[0110] Example 8 Hereinafter, a description will be given of an inverter device 80 according to the eighth embodiment. Since the configuration of the inverter device 80 is the same as that of the inverter device 20 according to the second embodiment, a detailed description of the circuit configuration will be omitted.

[0111] When the inverter device 80 is operated as a single-phase two-wire inverter device during grid-connection or the like, the neutral point control auxiliary circuit 22 is stopped and the switches SW3 and SW4 are turned off. At this time, the operations of the U-phase leg Lgu, the W-phase leg Lgw, the HERIC circuits 12 and 13 are controlled by the same PWM pattern as in a normal single-phase two-wire inverter device. Here, the HERIC circuits 12 and 13 perform the same operation.

[0112] A relay may be provided on the O-phase neutral wire Lio between the midpoint of HERIC circuit 12 and HERIC circuit 13 and output terminal Oo, and when inverter device 70 is operated as a single-phase two-wire inverter device during system interconnection or the like, this relay may be opened to interrupt the circuit.

[0113] In this way, efficient power conversion is possible even when the inverter device 80 is operated as a single-phase two-wire inverter device during system interconnection or the like.

[0114] Example 9 An inverter device 90 according to a ninth embodiment will be described below. Fig. 18 shows a circuit configuration of the inverter device 90. The same components as those in the first embodiment will be designated by the same reference numerals and detailed description will be omitted. The circuit configuration of the inverter device 90 includes a HERIC circuit 15 capable of short-circuiting the U-phase power line Liu and the W-phase power line Liw of the inverter device 90, and a load RLuw is connected between an output end Ou of the U-phase power line Liu and an output end Ow of the W-phase power line Liw. Here, the HERIC circuit 15 corresponds to the third short-circuit circuit of the present invention.

[0115] In the following, the parts of the circuit configuration of the inverter device 90 that differ from the inverter device 10 will be described. In the inverter device 90, the DC power supply connected to the input terminal Ip and the input terminal In is composed of two DC power supplies Sd1 and Sd2 with a midpoint. As described above, the HERIC circuit 15 is provided between the U-phase power line Liu and the W-phase power line Liw. The HERIC circuit 15 is provided between the HERIC circuits 12 and 13 and the reactors Lu and Lw. The HERIC circuit 15 includes switches SWuwn and SWuwp composed of n-channel enhancement type MOSFETs. Although omitted in FIG. 18, the HERIC circuit 15 has a gate drive circuit that drives the gates of the switches SWuwn and SWuwp, and the gate drive circuit controls the on / off of the switches SWuwn and SWuwp based on instructions from the control unit 16 that controls the operation of the inverter device 70. In addition, a capacitor Cuw and a load RLiw are connected in parallel between the output terminal Ou and the output terminal Ow.

[0116] In this way, in the inverter device 90, by providing the HERIC circuit 15, when short-circuiting the U-phase power line Liu and the W-phase power line Liw, the short-circuiting can be performed by a single HERIC circuit 15, thereby improving efficiency, compared to when the short-circuiting is performed by two HERIC circuits, that is, the HERIC circuit 12 which short-circuits the U-phase power line Liu and the O-phase neutral wire Lio, and the HERIC circuit 13 which short-circuits the O-phase neutral wire Lio and the W-phase power line Liw.

[0117] Example 10 Hereinafter, a description will be given of an inverter device 100 according to an embodiment 10. The configuration of the inverter device 100 is the same as that of the inverter device 90 according to an embodiment 9, so a detailed description of the circuit configuration will be omitted.

[0118] When the inverter device 100 is operated as a single-phase two-wire inverter device, the HERIC circuit 12 connected between the U-phase power line Liu and the O-phase neutral line Lio and the HERIC circuit 13 connected between the O-phase neutral line Lio and the W-phase power line Liw are stopped, and the HERIC circuit 15 connected between the U-phase power line Liu and the W-phase power line Liw is operated. This reduces the number of elements through which a current flows when the U-phase power line Liu and the W-phase power line Liw are short-circuited, thereby reducing switching loss and improving switching noise. In addition, since the inverter device 100 operates as a single-phase two-wire inverter device at this time, the phase difference between the U phase and the W phase is 180 degrees.

[0119] Example 11 Hereinafter, a description will be given of an inverter device 110 according to an eleventh embodiment. Since the configuration of the inverter device 110 is the same as that of the inverter device 90 according to the ninth embodiment, a detailed description of the circuit configuration will be omitted.

[0120] When inverter device 110 is operated as a single-phase two-wire inverter device, HERIC circuit 12 connected between U-phase power line Liu and O-phase neutral line Lio, HERIC circuit 13 connected between O-phase neutral line Lio and W-phase power line Liw, and HERIC circuit 15 connected between U-phase power line Liu and W-phase power line Liw are operated simultaneously. As a result, when the U-phase power line Liu and the W-phase power line Liw are short-circuited, current flows through the parallel paths of HERIC circuit 12, HERIC circuit 13, and HERIC circuit 15, thereby reducing conduction loss and improving efficiency.

[0121] <Appendix 1> An inverter device (10) that converts input DC power into single-phase three-wire AC power and outputs the AC power, A first phase output terminal (Ou), a second phase output terminal (Ow) and a neutral output terminal (Oo); an inverter unit (11) that converts the DC power into the AC power; a first-phase power line (Liu) connecting the inverter unit (11) and the first-phase output terminal (Ou) and receiving the first-phase power of the AC power; a second-phase power line (Liw) connecting the inverter unit (11) and the second-phase output terminal (Ow) and receiving the second-phase power of the AC power; a neutral power line (Lio) connecting the inverter unit (11) and the neutral output terminal (Oo); a first short circuit (12) connected between the first phase power line (Liu) and the neutral power line (Lio) and capable of short-circuiting between the first phase power line (Liu) and the neutral power line (Lio); , a second short circuit (13) connected between the second-phase power line (Liw) and the neutral power line (Lio) and capable of short-circuiting between the second-phase power line (Liw) and the neutral power line (Lio); a control unit (14) that controls the inverter unit (11), the first short circuit (12), and the second short circuit (13); An inverter device (10) comprising: [Explanation of symbols]

[0122] 10: Inverter device 11: Inverter 12,13:HERIC circuit Ou, Ow, Oo: Output terminal Liu :U phase power line Liw :W phase power line Lio :O phase neutral wire

Claims

1. An inverter device that converts input DC power into single-phase three-wire AC power and outputs the AC power, a first phase output terminal, a second phase output terminal, and a neutral output terminal; an inverter unit that converts the DC power into the AC power; a first-phase power line connecting the inverter unit and the first-phase output terminal and through which first-phase power of the AC power is supplied; a second-phase power line connecting the inverter unit and the second-phase output terminal and through which second-phase power of the AC power is supplied; a neutral power line connecting the inverter unit and the neutral output terminal; a first short circuit connected between the first phase power line and the neutral power line and capable of short-circuiting the first phase power line and the neutral power line; a second short circuit connected between the second phase power line and the neutral power line and capable of short-circuiting the second phase power line and the neutral power line; a first-phase reactor connected in series to the first-phase power line on the first-phase output terminal side of the first short circuit; a second-phase reactor connected in series to the second-phase power line on the second-phase output terminal side of the second short circuit; a neutral reactor connected in series to the neutral power line on the neutral output terminal side of the first short circuit and the second short circuit; a control unit that controls the inverter unit, the first short circuit, and the second short circuit, The inverter unit is A positive input terminal connected to a positive terminal of a DC power supply and a negative input terminal connected to a negative terminal of the DC power supply are connected in parallel. a first phase leg in which a first switching element connected to the positive input terminal and a second switching element connected to the negative input terminal are connected in series; a neutral leg in which a third switching element connected to the positive input terminal and a fourth switching element connected to the negative input terminal are connected in series; a second phase leg in which a fifth switching element connected to the positive input terminal and a sixth switching element connected to the negative input terminal are connected in series; having the first phase leg has a first phase connection point to which the first phase power line is connected at a midpoint between the first switching element and the second switching element, the neutral leg has a neutral connection point to which the neutral power line is connected at a midpoint between the third switching element and the fourth switching element, the second phase leg has a second phase connection point to which the second phase power line is connected at a midpoint between the fifth switching element and the sixth switching element, the first short circuit includes a first short-circuit switching element that switches on and off a current flowing from the neutral power line side to the first phase power line side, and a second short-circuit switching element that switches on and off a current flowing from the first phase power line side to the neutral power line side, the second short circuit includes a third short-circuit switching element that switches on and off a current flowing from the second phase power line side to the neutral power line side, and a fourth short-circuit switching element that switches on and off a current flowing from the neutral power line side to the second phase power line side, The PWM control of the first switching element to the sixth switching element by the control unit in one half cycle of the frequency of the AC power to be output is turning on the first switching element and turning off the second switching element; turning off the third switching element and turning on the fourth switching element; turning off the fifth switching element and turning on the sixth switching element; turning on the first short-circuit switching element; a first mode in which the third short-circuit switching element is turned on; turning on the first switching element and turning off the second switching element; turning on the third switching element and turning off the fourth switching element; turning off the fifth switching element and turning on the sixth switching element; turning on the first short-circuit switching element; a second mode in which the third short-circuit switching element is turned on; turning off the first switching element and the second switching element; turning off the third switching element and the fourth switching element; turning off the fifth switching element and the sixth switching element; turning on the first short-circuit switching element; a third mode in which the third short-circuit switching element is turned on; and including control for repeating transitions in the order of the first mode, the second mode, and the third mode.

2. An inverter device that converts input DC power into single-phase three-wire AC power and outputs the AC power, a first phase output terminal, a second phase output terminal, and a neutral output terminal; an inverter unit that converts the DC power into the AC power; a first-phase power line connecting the inverter unit and the first-phase output terminal and through which first-phase power of the AC power is supplied; a second-phase power line connecting the inverter unit and the second-phase output terminal and through which second-phase power of the AC power is supplied; a neutral power line connecting the inverter unit and the neutral output terminal; a first short circuit connected between the first phase power line and the neutral power line and capable of short-circuiting the first phase power line and the neutral power line; a second short circuit connected between the second phase power line and the neutral power line and capable of short-circuiting the second phase power line and the neutral power line; a first-phase reactor connected in series to the first-phase power line on the first-phase output terminal side of the first short circuit; a second-phase reactor connected in series to the second-phase power line on the second-phase output terminal side of the second short circuit; a control unit that controls the inverter unit, the first short circuit, and the second short circuit, The inverter unit is A positive input terminal connected to a positive terminal of a DC power supply and a negative input terminal connected to a negative terminal of the DC power supply are connected in parallel. a first phase leg in which a first switching element connected to the positive input terminal and a second switching element connected to the negative input terminal are connected in series; a neutral point circuit in which a first constant voltage source connected to the positive input terminal and a second constant voltage source connected to the negative input terminal are connected in series; a second phase leg in which a fifth switching element connected to the positive input terminal and a sixth switching element connected to the negative input terminal are connected in series; having the first phase leg has a first phase connection point to which the first phase power line is connected at a midpoint between the first switching element and the second switching element, the neutral point circuit has a neutral connection point to which the neutral power line is connected at a midpoint between the first constant voltage source and the second constant voltage source, the second phase leg has a second phase connection point to which the second phase power line is connected at a midpoint between the fifth switching element and the sixth switching element, the neutral point circuit includes: a third switching element connected to the positive side input terminal; a fourth switching element connected in series to the third switching element via a second neutral connection point and connected to the negative side input terminal; and a neutral reactor connected in series between the neutral connection point and the second neutral connection point; the first short circuit includes a first short-circuit switching element that switches on and off a current flowing from the neutral power line side to the first phase power line side, and a second short-circuit switching element that switches on and off a current flowing from the first phase power line side to the neutral power line side, the second short circuit includes a third short-circuit switching element that switches on and off a current flowing from the second phase power line side to the neutral power line side, and a fourth short-circuit switching element that switches on and off a current flowing from the neutral power line side to the second phase power line side, The PWM control of the first switching element to the sixth switching element by the control unit in one half cycle of the frequency of the AC power to be output is turning on the first switching element and turning off the second switching element; turning off the third switching element and turning on the fourth switching element; turning off the fifth switching element and turning on the sixth switching element; turning on the first short-circuit switching element; a first mode in which the third short-circuit switching element is turned on; turning on the first switching element and turning off the second switching element; turning on the third switching element and turning off the fourth switching element; turning off the fifth switching element and turning on the sixth switching element; turning on the first short-circuit switching element; a second mode in which the third short-circuit switching element is turned on; turning off the first switching element and the second switching element; turning off the third switching element and the fourth switching element; turning off the fifth switching element and the sixth switching element; turning on the first short-circuit switching element; a third mode in which the third short-circuit switching element is turned on; and including control for repeating transitions in the order of the first mode, the second mode, and the third mode.

3. The PWM control of the first switching element to the sixth switching element by the control unit in the other half cycle of the frequency of the AC power to be output is In the first mode and the second mode, The first switching element and the fifth switching element are switched on and off, The second switching element and the sixth switching element are switched on and off, The third switching element and the fourth switching element are switched on and off, turning on the second short-circuit switching element; a first-2 mode and a second-2 mode in which the fourth short-circuit switching element is turned on; turning off the first switching element and the second switching element; turning off the third switching element and the fourth switching element; turning off the fifth switching element and the sixth switching element; turning on the second short-circuit switching element; a 3-2 mode in which the fourth short-circuit switching element is turned on; 3. The inverter device according to claim 1, further comprising a control for repeating a transition in the order of the 1-2 mode, the 2-2 mode, and the 3-2 mode.

4. An inverter device that converts input DC power into single-phase three-wire AC power and outputs the AC power, a first phase output terminal, a second phase output terminal, and a neutral output terminal; an inverter unit that converts the DC power into the AC power; a first-phase power line connecting the inverter unit and the first-phase output terminal and through which first-phase power of the AC power is supplied; a second-phase power line connecting the inverter unit and the second-phase output terminal and through which second-phase power of the AC power is supplied; a neutral power line connecting the inverter unit and the neutral output terminal; a first short circuit connected between the first phase power line and the neutral power line and capable of short-circuiting the first phase power line and the neutral power line; a second short circuit connected between the second phase power line and the neutral power line and capable of short-circuiting the second phase power line and the neutral power line; a first-phase reactor connected in series to the first-phase power line on the first-phase output terminal side of the first short circuit; a second-phase reactor connected in series to the second-phase power line on the second-phase output terminal side of the second short circuit; a neutral reactor connected in series to the neutral power line on the neutral output terminal side of the first short circuit and the second short circuit; a control unit that controls the inverter unit, the first short circuit, and the second short circuit, The inverter unit is A positive input terminal connected to a positive terminal of a DC power supply and a negative input terminal connected to a negative terminal of the DC power supply are connected in parallel. a first phase leg in which a first switching element connected to the positive input terminal and a second switching element connected to the negative input terminal are connected in series; a neutral leg in which a third switching element connected to the positive input terminal and a fourth switching element connected to the negative input terminal are connected in series; a second phase leg in which a fifth switching element connected to the positive input terminal and a sixth switching element connected to the negative input terminal are connected in series; having the first phase leg has a first phase connection point to which the first phase power line is connected at a midpoint between the first switching element and the second switching element, The neutral leg is provided at a midpoint between the third switching element and the fourth switching element. a neutral connection point to which the neutral power line is connected; the second phase leg has a second phase connection point to which the second phase power line is connected at a midpoint between the fifth switching element and the sixth switching element, the first short circuit includes a first short-circuit switching element that switches on and off a current flowing from the neutral power line side to the first phase power line side, and a second short-circuit switching element that switches on and off a current flowing from the first phase power line side to the neutral power line side, the second short circuit includes a third short-circuit switching element that switches on and off a current flowing from the second phase power line side to the neutral power line side, and a fourth short-circuit switching element that switches on and off a current flowing from the neutral power line side to the second phase power line side, The PWM control of the first switching element to the sixth switching element by the control unit in one half cycle of the frequency of the AC power to be output is turning on the first switching element and turning off the second switching element; turning off the third switching element and turning on the fourth switching element; turning off the fifth switching element and turning on the sixth switching element; turning on the first short-circuit switching element; a fourth mode in which the third short-circuit switching element is turned on; turning on the first switching element and turning off the second switching element; turning on the third switching element and turning off the fourth switching element; turning off the fifth switching element and turning on the sixth switching element; turning on the first short-circuit switching element; a fifth mode in which the third short-circuit switching element is turned on; turning off the first switching element and turning on the second switching element; turning on the third switching element and turning off the fourth switching element; The fifth switching element is turned on and the sixth switching element is turned off; turning on the first short-circuit switching element; a sixth mode in which the third short-circuit switching element is turned on; turning off the first switching element and turning on the second switching element; turning off the third switching element and turning on the fourth switching element; The fifth switching element is turned on and the sixth switching element is turned off; turning on the first short-circuit switching element; a seventh mode in which the third short-circuit switching element is turned on; and including control for repeating transitions in the order of the fourth mode, the fifth mode, the sixth mode, and the seventh mode.

5. An inverter device that converts input DC power into single-phase three-wire AC power and outputs the converted power, a first phase output terminal, a second phase output terminal, and a neutral output terminal; an inverter unit that converts the DC power into the AC power; a first-phase power line connecting the inverter unit and the first-phase output terminal and through which first-phase power of the AC power is supplied; a second-phase power line connecting the inverter unit and the second-phase output terminal and through which second-phase power of the AC power is supplied; a neutral power line connecting the inverter unit and the neutral output terminal; a first short circuit connected between the first phase power line and the neutral power line and capable of short-circuiting the first phase power line and the neutral power line; a second short circuit connected between the second phase power line and the neutral power line and capable of short-circuiting the second phase power line and the neutral power line; a first-phase reactor connected in series to the first-phase power line on the first-phase output terminal side of the first short circuit; A second short circuit is connected to the second phase output terminal side of the second short circuit in series with the second phase power line. A two-phase reactor; a control unit that controls the inverter unit, the first short circuit, and the second short circuit, The inverter unit is A positive input terminal connected to a positive terminal of a DC power supply and a negative input terminal connected to a negative terminal of the DC power supply are connected in parallel. a first phase leg in which a first switching element connected to the positive input terminal and a second switching element connected to the negative input terminal are connected in series; a neutral point circuit in which a first constant voltage source connected to the positive input terminal and a second constant voltage source connected to the negative input terminal are connected in series; a second phase leg in which a fifth switching element connected to the positive input terminal and a sixth switching element connected to the negative input terminal are connected in series; having the first phase leg has a first phase connection point to which the first phase power line is connected at a midpoint between the first switching element and the second switching element, the neutral point circuit has a neutral connection point to which the neutral power line is connected at a midpoint between the first constant voltage source and the second constant voltage source, the second phase leg has a second phase connection point to which the second phase power line is connected at a midpoint between the fifth switching element and the sixth switching element, the neutral point circuit includes: a third switching element connected to the positive side input terminal; a fourth switching element connected in series to the third switching element via a second neutral connection point and connected to the negative side input terminal; and a neutral reactor connected in series between the neutral connection point and the second neutral connection point; the first short circuit includes a first short-circuit switching element that switches on and off a current flowing from the neutral power line side to the first phase power line side, and a second short-circuit switching element that switches on and off a current flowing from the first phase power line side to the neutral power line side, the second short circuit includes a third short-circuit switching element that switches on and off a current flowing from the second phase power line side to the neutral power line side, and a fourth short-circuit switching element that switches on and off a current flowing from the neutral power line side to the second phase power line side, The PWM control of the first switching element to the sixth switching element by the control unit in one half cycle of the frequency of the AC power to be output is turning on the first switching element and turning off the second switching element; turning off the third switching element and turning on the fourth switching element; turning off the fifth switching element and turning on the sixth switching element; turning on the first short-circuit switching element; a fourth mode in which the third short-circuit switching element is turned on; turning on the first switching element and turning off the second switching element; turning on the third switching element and turning off the fourth switching element; turning off the fifth switching element and turning on the sixth switching element; turning on the first short-circuit switching element; a fifth mode in which the third short-circuit switching element is turned on; turning off the first switching element and turning on the second switching element; turning on the third switching element and turning off the fourth switching element; The fifth switching element is turned on and the sixth switching element is turned off; turning on the first short-circuit switching element; a sixth mode in which the third short-circuit switching element is turned on; turning off the first switching element and turning on the second switching element; turning off the third switching element and turning on the fourth switching element; The fifth switching element is turned on and the sixth switching element is turned off; turning on the first short-circuit switching element; a seventh mode in which the third short-circuit switching element is turned on; and including control for repeating transitions in the order of the fourth mode, the fifth mode, the sixth mode, and the seventh mode.

6. The PWM control of the first switching element to the sixth switching element by the control unit in the other half cycle of the frequency of the AC power to be output is In the fourth mode, the fifth mode, the sixth mode, and the seventh mode, The first switching element and the fifth switching element are switched on and off, The third switching element and the fourth switching element are switched on and off, The second switching element and the sixth switching element are switched on and off, turning on the second short-circuit switching element; The inverter device according to claim 4 or 5, characterized in that it includes a 4-2 mode, a 5-2 mode, a 6-2 mode, and a 7-2 mode in which the fourth short-circuit switching element is turned on, and includes control for repeating transitions in the order of the 4-2 mode, the 5-2 mode, the 6-2 mode, and the 7-2 mode.

7. the first switching element and the second switching element; The first short circuit; A first single-phase two-wire inverter module including: the fifth switching element and the sixth switching element; The second short circuit; a second single-phase two-wire inverter module including: Including, 5. The inverter device according to claim 1, wherein at least one of the first single-phase two-wire inverter module and the second single-phase two-wire inverter module includes the third switching element and the fourth switching element.

8. The first switching element and the second switching element, The first short circuit; a third single-phase two-wire inverter module including: the fifth switching element and the sixth switching element; The second short circuit; A fourth single-phase two-wire inverter module including: Including, 6. The inverter device according to claim 2, wherein either the third single-phase two-wire inverter module or the fourth single-phase two-wire inverter module includes the third switching element and the fourth switching element.

9. The control unit is turning off the third switching element and the fourth switching element of the neutral leg; 2. The inverter device according to claim 1, further comprising a mode in which the first switching element and the second switching element of the first phase leg and the fifth switching element and the sixth switching element of the second phase leg are PWM controlled.

10. The control unit: turning off the third switching element and the fourth switching element of the neutral point circuit; 3. The inverter device according to claim 2, further comprising a mode in which the first switching element and the second switching element of the first phase leg and the fifth switching element and the sixth switching element of the second phase leg are PWM controlled.

11. a third short circuit connected between the first-phase power line and the second-phase power line and capable of short-circuiting the first-phase power line and the second-phase power line; 7. The inverter device according to claim 1, wherein the control unit controls the third short circuit.

12. The control unit: turning off the third switching element and the fourth switching element; When the first switching element and the second switching element of the first phase leg and the fifth switching element and the sixth switching element of the second phase leg are PWM controlled, 12. The inverter device according to claim 11, wherein the first short circuit and the second short circuit are stopped, and the third short circuit is operated.

13. The control unit: turning off the third switching element and the fourth switching element; When the first switching element and the second switching element of the first phase leg and the fifth switching element and the sixth switching element of the second phase leg are PWM controlled, 12. The inverter device according to claim 11, wherein the first short circuit, the second short circuit, and the third short circuit are activated.

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