JP2015204637A - Power conversion apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce loss of a converter.SOLUTION: Each of a converter 110 and an inverter 130 includes a plurality of arm circuits 115(1), 115(2), ..., 115(n) connected in parallel, each of the arm circuits includes at least two or more switching circuits 117(11), 117(12) connected in series, and each of the switching circuits includes a rectifier element and a switching element connected in parallel. When a synchronization/phase coincidence detection unit detects synchronization between AC voltage of an AC input terminal and AC voltage of an AC output terminal and coincidence of phases, a switch excitation unit closes a switch 145 and a converter control unit controls a current flowing into one arm circuit 115(1) of the converter to 0.

Description

  The present invention relates to a power conversion device including a PWM-controlled converter and an inverter, and more particularly to a power conversion device that can reduce converter loss.

  As shown in Patent Document 1 below, a conventional power converter includes a converter that converts AC power into DC power, and an inverter that converts DC power output from the converter into predetermined AC power.

  The converter is configured as follows. The rectifying element and the switching element are connected in parallel to form a switching circuit. At least two or more switching circuits are connected in series to constitute an arm circuit. A plurality of arm circuits are connected in parallel to form a converter.

  The inverter is configured as follows. The rectifying element and the switching element are connected in parallel to form a switching circuit. At least two or more switching circuits are connected in series to constitute an arm circuit. The plurality of arm circuits are connected in parallel to form an inverter.

  The converter and the inverter have the same configuration as described above, but the operation of the converter is controlled by the converter drive circuit, and the operation of the inverter is controlled by the inverter drive circuit.

Japanese Patent No. 3588932 Specification

  As described above, the conventional power conversion device includes the converter and the inverter, and when the power conversion device operates, a current flows through all the switching circuits constituting each arm circuit. For this reason, many losses, such as a conduction loss of a switching element and a switching loss, have occurred at the time of operation of a power converter.

  The power converter provided in the uninterruptible power supply is operated by synchronizing the input voltage and the output voltage. Therefore, when the input voltage of the inverter and the output voltage of the converter are synchronized, the loss of the power converter should be reduced by directly connecting the inverter arm circuit and the converter arm circuit.

  The present invention has been made based on the above-described idea, and in particular, an object of the present invention is to provide a power conversion device that can reduce the loss of a converter.

  In order to achieve the above object, a power conversion device according to the present invention includes a converter, an inverter, a switch excitation unit, a synchronization / phase matching detection unit, and a converter control unit.

  The converter converts AC power input from the AC input terminal into DC power. The inverter converts DC power input from the converter into AC power and outputs the AC power from the AC output terminal. The switch excitation unit opens and closes a switch provided between the AC input terminal and the AC output terminal. The synchronization / phase matching detection unit detects synchronization and phase matching between the AC voltage at the AC input terminal and the AC voltage at the AC output terminal. The converter control unit controls the operation of the converter. The converter and the inverter have a plurality of arm circuits connected in parallel, the arm circuit has at least two or more switching circuits connected in series, and the switching circuit includes a rectifying element connected in parallel and A switching element, and when the synchronization / phase matching detection unit detects synchronization and phase matching between the AC voltage at the AC input terminal and the AC voltage at the AC output terminal, the switch excitation unit closes the switch, and the converter control unit Control is performed so that the current flowing through one arm circuit of the converter becomes zero.

  According to the power conversion device according to the present invention configured as described above, when the synchronization and phase matching of the AC voltage of the AC input terminal and the AC voltage of the AC output terminal are detected, the AC input terminal of the converter and the inverter Since the current flowing through one arm circuit of the converter becomes zero, the converter loss can be reduced.

It is a schematic block diagram of the power converter device which concerns on Embodiment 1 and 2. FIG. It is a block diagram of the control part of the power converter device concerning Embodiment 1. FIG. It is operation | movement explanatory drawing of the conventional power converter device. It is operation | movement explanatory drawing of the power converter device which concerns on Embodiment 1. FIG. It is operation | movement explanatory drawing of the power converter device which concerns on Embodiment 1. FIG. It is a block diagram of the control part of the power converter device concerning Embodiment 2. It is a schematic block diagram of the power converter device which concerns on Embodiment 3 and 4. FIG. It is a block diagram of the control part of the power converter device concerning Embodiment 3. It is a block diagram of the control part of the power converter device concerning Embodiment 4.

  Hereinafter, embodiments of a power conversion device according to the present invention will be described by dividing them from [Embodiment 1] to [Embodiment 4].

[Embodiment 1]
FIG. 1 is a schematic configuration diagram of a power conversion device according to the first embodiment. The power conversion apparatus 100 includes a converter 110, an inverter 130, and a control unit 150.

[Configuration of power converter]
<Configuration of converter and inverter>
Converter 110 has arm circuits 115 (1), 115 (2),..., 115 (n). Arm circuits 115 (1), 115 (2),..., 115 (n) are connected in parallel. Each arm circuit 115 (1), 115 (2),..., 115 (n) has two switching circuits connected in series. The arm circuit 115 (1) has switching circuits 117 (11) and 117 (12), the arm circuit 115 (2) has switching circuits 117 (21) and 117 (22),... 115 (n) includes switching circuits 117 (n1) and 117 (n2). Each switching circuit 117 (11), 117 (12), 117 (21), 117 (22),..., 117 (n1) and 117 (n2) is composed of a rectifying element and a switching element connected in parallel. .

  Converter 110 includes a reactor 118 (1) connected to arm circuit 115 (1), a reactor 118 (2) connected to arm circuit 115 (2), and a reactor connected to arm circuit 115 (n). 118 (n). Reactors 118 (1), 118 (2),..., 118 (n) constitute a filter circuit.

  Converter 110 is connected to AC input terminals IN (1), IN (2), ..., IN (n) via reactors 118 (1), 118 (2), ..., 118 (n). Converter 110 converts the input AC power into DC power by the switching operation of each switching element, and outputs the converted DC power.

  The inverter 130 includes arm circuits 135 (1), 135 (2),..., 135 (n). The arm circuits 135 (1), 135 (2),..., 135 (n) are connected in parallel. Each arm circuit 135 (1), 135 (2),..., 135 (n) has two switching circuits connected in series. The arm circuit 135 (1) has switching circuits 137 (11) and 137 (12), the arm circuit 135 (2) has switching circuits 137 (21) and 137 (22),... 135 (n) includes switching circuits 137 (n1) and 137 (n2). Each of the switching circuits 137 (11), 137 (12), 137 (21), 137 (22), ..., 137 (n1) and 137 (n2) is composed of a rectifying element and a switching element connected in parallel. .

  The inverter 130 includes a reactor 138 (1) and a capacitor 139 (1) connected to the arm circuit 135 (1), a reactor 138 (2) and a capacitor 139 (2) connected to the arm circuit 135 (2),. And a reactor 138 (n) and a capacitor 139 (n) connected to the arm circuit 135 (n). Capacitors 139 (1), 139 (2),..., And 139 (n) are star connected. Reactors 138 (1), 138 (2), ..., 138 (n) and capacitors 139 (1), 139 (2), ..., 139 (n) constitute a filter circuit.

  Inverter 130 is connected to AC output terminals OUT (1), OUT (2),..., OUT (n) via reactors 138 (1), 138 (2),. The inverter 130 converts the input DC power into AC power by the switching operation of each switching element, and outputs the converted AC power to the AC output terminals OUT (1), OUT (2),..., OUT (n). To do.

  A smoothing capacitor 140 is connected between the converter 110 and the inverter 130. A switch 145 is connected between the AC input terminal IN (1) of the converter 110 and the AC output terminal OUT (1) of the inverter 130. When switch 145 is closed, AC input terminal IN (1) of converter 110 and AC output terminal OUT (1) of inverter 130 are directly connected. Therefore, the switch 145 connects the arm circuits 115 (1) and 135 (1) of the same phase.

  The control unit 150 controls the operation of the converter 110 and the inverter 130 and the opening / closing of the switch 145. Converter 110 and inverter 130 are PWM-controlled by control unit 150. The switch 145 is closed by the control unit 150 when both AC voltages of the AC input terminal IN (1) and the AC output terminal OUT (1) are synchronized and in phase. The switch 145 is opened by the control unit 150 when both AC voltages are not synchronized or their phases do not match. The controller 150 controls the switching operation of the switching circuits 117 (11) and 117 (12) so that the current flowing through the arm circuit 115 (1) becomes 0 simultaneously with closing the switch 145. For this reason, the current flowing from the AC input terminal IN (1) into the arm circuit 115 (1) becomes zero. The current from the AC input terminal IN (1) flows to the AC output terminal OUT (1) via the switch 145.

<Configuration of control unit>
FIG. 2 is a block diagram of the control unit 150 of the power conversion apparatus 100 according to the first embodiment. The control unit 150 includes a converter control unit 160, an inverter control unit 170, a synchronization / phase matching detection circuit 180, and a SW excitation circuit 190.

  Converter control unit 160 includes an input current amplitude command generation circuit 161, an input current reference sine wave generation circuit 162, a switch 163, a converter phase voltage modulation command generation circuit 164, a PWM signal generation circuit 165, and a converter drive circuit 166.

  Input current amplitude command generation circuit 161 inputs DC voltage VDC that converter 110 actually outputs and DC reference voltage VDCref as a reference voltage to be output from converter 110. Input current amplitude command generation circuit 161 outputs an input current amplitude command for making DC voltage VDC output from converter 110 coincide with DC reference voltage VDCref.

  The input current reference sine wave generation circuit 162 has input phase voltages VIN (1), VIN (2),... Input to AC input terminals IN (1), IN (2),. VIN (N) and the input current amplitude command output from the input current amplitude command generation circuit 161 are input. The input current reference sine wave generation circuit 162 uses the input phase voltages VIN (1), VIN (2),... VIN (N) and the input current amplitude command to input the input phase voltages VIN (1), VIN (2), ... generates an input current reference sine wave in phase with VIN (N). The input current reference sine wave for the arm circuit 115 (1) is output to the switch 163. The input current reference sine wave for arm circuits 115 (2),..., 115 (n) is output to converter phase voltage modulation command generation circuit 164. The input current reference sine wave for each arm circuit 115 (1), 115 (2),..., 115 (n) is independently generated.

  The switch 163 switches between an input current reference sine wave and a 0 V input current reference sine wave in response to a SW excitation signal output from a synchronization / phase matching detection circuit 180 described later. The switch 163 outputs a 0V input current reference sine wave when the SW excitation signal is output, and outputs an input current reference sine wave when the SW excitation signal is not output.

  Converter phase voltage modulation command generation circuit 164 includes input currents Iconv (1), IIN (2),..., Input to AC input terminals IN (1), IN (2),. Enter IIN (n). Further, converter phase voltage modulation command generation circuit 164 inputs 0 V input current reference sine wave or input current reference sine wave to arm circuit 115 (1) via switch 163. Further, converter phase voltage modulation command generation circuit 164 receives input current reference sine waves corresponding to arm circuits 115 (2),..., 115 (n), respectively. The converter phase voltage modulation command generation circuit 164 uses the input currents Iconv (1), IIN (2),..., IIN (n), the input current reference sine wave, and the 0V input current reference sine wave to input each input voltage. Let Iconv (1), IIN (2),..., IIN (n) match the input current reference sine wave of the phase corresponding to the respective input voltages Iconv (1), IIN (2),. Converter phase voltage modulation command is generated and output to the PWM signal generation circuit 165.

  The PWM signal generation circuit 165 uses the converter phase voltage modulation command output from the converter phase voltage modulation command generation circuit 164 to generate PWM signals for the arm circuits 115 (1), 115 (2),..., 115 (n). Output.

  The converter drive circuit 166 switches the switching elements of the arm circuits 115 (1), 115 (2),..., 115 (n) using the PWM signal output from the PWM signal generation circuit 165.

  The inverter control unit 170 includes a PLL circuit 171, an oscillator 172, a switching circuit 173, an inverter voltage reference sine wave generation circuit 174, an inverter phase voltage modulation command generation circuit 175, a PWM signal generation circuit 176, and an inverter drive circuit 177.

  The PLL circuit 171 receives the input phase voltage VIN (1) input to the converter 110, and outputs a new signal synchronized with the phase of the input phase voltage VIN (1).

  The oscillator 172 outputs a signal having a predetermined frequency.

  The switching circuit 173 switches between a signal output from the PLL circuit 171 and a signal output from the oscillator 172 in response to a SW excitation signal output from a synchronization / phase matching detection circuit 180 described later. The switching circuit 173 outputs a signal output from the PLL circuit 171 when the SW excitation signal is output, and outputs a signal output from the oscillator 172 when the excitation signal is not output.

  The inverter voltage reference sine wave generation circuit 174 receives the signal output from the switching circuit 173 and outputs an inverter voltage reference sine wave.

  The inverter phase voltage modulation command generation circuit 175 includes output voltages VOUT (1), VOUT (2),... Output from the AC output terminals OUT (1), OUT (2),. Input VOUT (n). Further, the inverter phase voltage modulation command generation circuit 175 receives the inverter voltage reference sine wave output from the inverter voltage reference sine wave generation circuit 174. The inverter phase voltage modulation command generation circuit 175 generates an inverter phase voltage modulation command so that the output voltages VOUT (1), VOUT (2),..., VOUT (n) and the inverter voltage reference sine wave coincide with each other. The signal is output to the signal generation circuit 176.

  The PWM signal generation circuit 176 uses the inverter phase voltage modulation command output from the inverter phase voltage modulation command generation circuit 175 to generate a PWM signal for the arm circuits 135 (1), 135 (2),..., 135 (n). Output.

  The inverter drive circuit 177 uses the PWM signal output from the PWM signal generation circuit 176 to switch the switching elements of the arm circuits 135 (1), 135 (2),..., 135 (n).

  The synchronization / phase matching detection circuit 180 has an input phase voltage VIN (1) input to the AC input terminal IN (1) of the converter 110 and an output voltage VOUT (1) output from the AC output terminal OUT (1) of the inverter 130. ). The synchronization / phase coincidence detection circuit 180 compares the synchronization state and the phase state of both voltages. The synchronization / phase coincidence detection circuit 180 outputs an SW excitation signal when both voltages are synchronized and the phases coincide. If both voltages are not synchronized or in phase, the SW excitation signal is not output.

  The SW excitation circuit 190 opens and closes the switch 145 (see FIG. 1) using the SW excitation signal output from the synchronization / phase matching detection circuit 180. The SW excitation circuit 190 closes the switch 145 when the SW excitation signal is output. When switch 145 is closed, AC input terminal IN (1) of converter 110 and AC output terminal OUT (1) of inverter 130 are directly connected, and arm circuits 115 (1) and 135 (1) having the same phase are connected. Connected. On the other hand, when the SW excitation signal is not output, the switch 145 is opened.

[Operation of power converter]
<When input phase voltage and output voltage are not synchronized or in phase>
When the input phase voltage VIN (1) and the output voltage VOUT (1) are not synchronized or in phase, the synchronization / phase matching detection circuit 180 does not output the SW excitation signal. Therefore, the switch 163 outputs the input current reference sine wave instead of the 0 V input current reference sine wave, the switch circuit 173 outputs the signal output from the oscillator 172, and the switch 145 (see FIG. 1) is the SW excitation circuit 190. Opened by.

  AC power is supplied to AC input terminals IN (1), IN (2),..., IN (n) of converter 110. Input current amplitude command generation circuit 161 compares DC voltage VDC output from converter 110 with DC reference voltage VDCref as a reference voltage to be output from converter 110 so that DC voltage VDC matches DC reference voltage VDCref. A simple input current amplitude command is generated. The input current amplitude command generation circuit 161 outputs the generated input current amplitude command to the input current reference sine wave generation circuit 162.

  The input current reference sine wave generation circuit 162 applies the input current amplitude command output from the input current amplitude command generation circuit 161 and the AC input terminals IN (1), IN (2),. An input current reference sine wave is generated using input phase voltages VIN (1), VIN (2),... VIN (N). The input current reference sine wave for arm circuit 115 (1) is output to switch 163, and the input current reference sine wave for arm circuits 115 (2),..., 115 (n) is output to converter phase voltage modulation command generation circuit 164. Is done.

  When the input phase voltage and the output voltage are not synchronized or the phases are not matched, the synchronization / phase match detection circuit 180 does not output the SW excitation signal. Therefore, switch 163 outputs the input current reference sine wave for arm circuit 115 (1) generated by input current reference sine wave generation circuit 162 to converter phase voltage modulation command generation circuit 164. Therefore, the converter phase voltage modulation command generation circuit 164 inputs the input current reference sine wave for the input currents Iconv (1), IIN (2),... IIN (n) generated by the input current reference sine wave generation circuit 162. Will do.

  Converter phase voltage modulation command generation circuit 164 receives input currents Iconv (1), IIN (2),..., IIN (n) from AC input terminals IN (1), IN (2),. ) And the input current reference sine wave generated by the input current reference sine wave generation circuit 162 is input to the arm circuits 115 (1), 115 (2),..., 115 (n). The converter phase voltage modulation command generation circuit 164 includes input currents Iconv (1), IIN (2),..., IIN (n) and arm circuits 115 (1), 115 (2),. Is used to generate a converter phase voltage modulation command. The generated converter phase voltage modulation command is output to PWM signal generation circuit 165.

  The PWM signal generation circuit 165 outputs a PWM signal for the arm circuits 115 (1), 115 (2),..., 115 (n) using the converter phase voltage modulation command generated by the converter phase voltage modulation command generation circuit 164. To do. Converter drive circuit 166 controls the switching elements of arm circuits 115 (1), 115 (2),..., 115 (n) of converter 110 to ON / OFF using PWM pulses.

  Therefore, converter 110 is controlled to convert AC power into DC power having a constant voltage and output the same.

  DC power output from the converter 110 is supplied to the inverter 130. The PLL circuit 171 uses the input phase voltage VIN (1) input to the AC input terminal IN (1) of the converter 110 to output a new signal synchronized with the phase of the input phase voltage VIN (1). The oscillator 172 outputs a signal having a predetermined frequency to the switching circuit 173.

  When the input phase voltage and the output voltage are not synchronized or the phases are not matched, the synchronization / phase match detection circuit 180 does not output the SW excitation signal. Therefore, switching circuit 173 outputs a signal output from oscillator 172.

  The inverter voltage reference sine wave generation circuit 174 receives a signal output from the oscillator 172 via the switching circuit 173 and outputs an inverter voltage reference sine wave so that a predetermined AC voltage is output from the inverter 130.

  The inverter phase voltage modulation command generation circuit 175 outputs the output voltages VOUT (1), VOUT (2),..., VOUT (n) from the AC output terminals OUT (1), OUT (2),. ) And the inverter voltage reference sine wave generation circuit 174 inputs the inverter voltage reference sine wave. The inverter phase voltage modulation command generation circuit 175 generates an inverter phase voltage modulation command using the output voltages VOUT (1), VOUT (2),..., VOUT (n) and the inverter voltage reference sine wave. The generated inverter phase voltage modulation command is output to PWM signal generation circuit 176.

  The PWM signal generation circuit 176 outputs a PWM signal for the arm circuits 135 (1), 135 (2),..., 135 (n) using the inverter phase voltage modulation command generated by the inverter phase voltage modulation command generation circuit 175. To do. The inverter drive circuit 177 performs ON / OFF control of the switching elements of the arm circuits 135 (1), 135 (2),..., 135 (n) of the inverter 130 using the PWM pulse.

  Therefore, the inverter 130 is controlled so as to convert the input DC power into a constant voltage AC power and output it.

  Thus, when the input phase voltage and the output voltage are not synchronized or in phase, the AC power input to the converter 110 passes through all the circuits of the converter 110 and has a predetermined voltage. The DC power input to the inverter 130 is converted into AC power having a predetermined voltage through all the circuits of the inverter 130. That is, converter 110 and inverter 130 operate normally.

<When input phase voltage and output voltage are synchronized and in phase>
When the input phase voltage VIN (1) and the output voltage VOUT (1) are synchronized and in phase, the synchronization / phase matching detection circuit 180 outputs a SW excitation signal. Therefore, the switch 163 outputs a 0V input current reference sine wave, the switch circuit 173 outputs a signal output from the PLL circuit 171, and the switch 145 (see FIG. 1) is closed by the SW excitation circuit 190.

  Even when the input phase voltage and the output voltage are synchronized and in phase, the input current amplitude command generation circuit 161, the input current reference sine wave generation circuit 162, the PWM signal generation circuit 165, the converter drive circuit 166, the PLL circuit 171, The operations of the oscillator 172, the inverter phase voltage modulation command generation circuit 175, the PWM signal generation circuit 176, and the inverter drive circuit 177 are performed when the input phase voltage and the output voltage are not synchronized or in phase. Is the same.

  When the input phase voltage and the output voltage are synchronized and in phase, the switch 163 outputs a 0 V input current reference sine wave instead of the input current reference sine wave.

  Converter phase voltage modulation command generation circuit 164 receives input currents Iconv (1), IIN (2),..., IIN (n) from AC input terminals IN (1), IN (2),. ) For the arm circuit 115 (1) generated by the input current reference sine wave generation circuit 162 and the 0 V input current reference sine wave for the arm circuit 115 (1) output by the switch 163 Input the input current reference sine wave. The converter phase voltage modulation command generation circuit 164 includes input currents Iconv (1), IIN (2),..., IIN (n), and a 0V input current reference sine wave for the arm circuit 115 (1), 115 (2). ,..., 115 (n) is used to generate a converter phase voltage modulation command using an input current reference sine wave. The generated converter phase voltage modulation command is output to PWM signal generation circuit 165.

  The switching circuits 117 (11) and 117 (12) of the arm circuit 115 (1) are switched by the converter driving circuit 166. However, the switching circuits 117 (11) and 117 (12) are switched using the 0V input current reference sine wave so that the input current Iconv (1) becomes the 0V input current reference sine wave. The current output from the arm circuit 115 (1) becomes zero. Therefore, the current Iconv (1) flowing into the arm circuit 115 (1) shown in FIG. 1 is always 0A.

  When the input phase voltage and the output voltage are synchronized and in phase, the switch 145 is closed. Since the current Iconv (1) is controlled to be 0 A, the current Isw flowing through the switch 145 shown in FIG. 1 is the same as the current Iconv (1) flowing from the AC input terminal IN (1). Become.

  When the input phase voltage and the output voltage are synchronized and in phase, the switching circuit 173 outputs a signal output from the PLL circuit 171. The inverter voltage reference sine wave generation circuit 174 receives a signal output from the PLL circuit 171 via the switching circuit 173, and outputs an inverter voltage reference sine wave so that a predetermined AC voltage is output from the inverter 130. .

  When the input phase voltage and the output voltage are synchronized and in phase, the fundamental frequency current of the commercial frequency does not flow through the arm circuit 115 (1). For this reason, only a small amount of switching current flows through the switching circuits 117 (11) and 117 (12) and the reactor 118 (1), and the conduction loss becomes almost zero.

  In this case, the arm circuit 135 (1) of the inverter 130 plays the role of the arm circuit 115 (1) of the converter 110. That is, the arm circuit 135 (1) of the inverter 130 becomes a shared arm of the arm circuit 115 (1) of the converter 110 and the arm circuit 135 (1) of the inverter 130.

  The operation of the converter 110 and the inverter 130 when the input phase voltage and the output voltage are synchronized and in phase with each other will be described in more detail with reference to FIGS.

  FIG. 3 is an operation explanatory diagram of the conventional power conversion device, and FIGS. 4 and 5 are operation explanatory diagrams of the power conversion device according to the first embodiment.

  As shown in FIG. 3, the conventional power conversion device has an arm circuit 115 (1) of the converter 110 with a dotted line as shown in FIG. Current flows. Therefore, current loss occurs in the switching elements of the arm circuit 115 (1) and the reactor 118 (1). In addition, switching loss due to the switching element of the arm circuit 115 (1) occurs.

  On the other hand, in the power conversion device according to the first embodiment, when the input phase voltage and the output voltage are synchronized and the phases coincide with each other, the switch 145 is closed as shown in FIG. When switch 145 is closed, AC input terminal IN (1) of converter 110 and AC output terminal OUT (1) of converter 130 are directly connected.

  Here, in order to control the input current Iconv (1) to be 0 A, the current input from the AC input terminal IN (1) passes through the switch 145 as shown by the solid line in FIG. The current flows to OUT (1), passes through the reactor 138 (1), and flows into the arm circuit 135 (1) and the smoothing capacitor 140.

  Thus, when the input phase voltage and the output voltage are synchronized and the phases match, no current flows into the arm circuit 115 (1) of the converter 110. Therefore, the switching element and the reactor 118 ( The energization loss of 1) is almost eliminated.

  In the case of the conventional power conversion device shown in FIG. 3, a current as shown by a dotted line in FIG. 5 flows from the arm circuit 135 (1) of the inverter 130 toward the AC output terminal OUT (1). However, in the power conversion device 100 according to the first embodiment, a current in a direction as illustrated in FIG. 4 flows toward the arm circuit 135 (1) of the inverter 130. Therefore, if the power factor of the load is 1, the current of FIG. 4 cancels the current of FIG. 5, and the fundamental wave of the commercial frequency flowing through the arm circuit 135 (1) and the reactance 138 (1) of the inverter 130. The effective value of becomes zero.

  When the power factor of the load is 1, the conduction loss of the switching element of the arm circuit 135 (1) of the inverter 130 and the reactor 138 (1) is almost eliminated. Even if the power factor is not 1, the conduction loss of the switching element of the arm circuit 135 (1) and the reactor 138 (1) is reduced to some extent depending on the magnitude of the power factor.

  Here, the current IIN (1), the current Iconv (1), and the current Isw will be described in more detail with reference to FIGS.

  When the switch 145 is closed, the current IIN (1) input from the AC input terminal IN (1) is the current Iconv (1) that flows in the path indicated by the dotted line in FIG. 3 and the current that flows in the path indicated by the dotted line in FIG. Is the sum of Isw. When this is expressed by an equation, IIN (1) = Iconv (1) + Isw.

  In the conventional control shown in FIG. 3, the current Iconv (1) is controlled to be equal to the input current reference sine wave (output from the input current reference sine wave generation circuit 162). This input current reference sine wave is the current of the arm circuit 115 (1) required by the converter 110 when the switch 145 is open. This is expressed by an equation: Iconv (1) = IIN (1). Therefore, even if the switch 145 is closed with the conventional control, the current Isw does not flow through the switch 145.

  Here, if the input current reference sine wave for Iconv (1) is set to 0V, then Iconv (1) = 0A, and from IIN (1) = Iconv (1) + Isw, IIN (1) = Isw and current IIN (1) flows through the switch 145 as a current Isw. Further, the current required for the other arm circuits 115 (2),..., 115 (n) of the converter 110 is controlled to be expressed by the following equation.

Current Iconv (2) of arm circuit 115 (2) = √2 * Iin * sin (θ−2π / n) = IIN (2)
Here, Iin is an effective value of current IIN required by converter 110. Current Iconv (n) of arm circuit 115 (n) = √2 * Iin * sin (θ−2 (n−1) π / n) = IIN (N)
Since IIN (1) = − IIN (2) −IIN (3)... −IN (n), IIN (1) = √2 * Iin * sin (θ) and current IIN (1) is input. It becomes a sine wave current in phase with the phase voltage of the terminal IN (1).

[Embodiment 2]
[Configuration of power converter]
<Configuration of converter and inverter>
FIG. 6 is a block diagram of a control unit of the power conversion apparatus according to the second embodiment. The configurations of the converter 110 and the inverter 130 of the power conversion device 100 according to the second embodiment are the same as the configurations of the converter 110 and the inverter 130 of the power conversion device 100 according to the first embodiment shown in FIG.

<Configuration of control unit>
In the power conversion device 100 according to the second embodiment, when the input phase voltage and the output voltage are synchronized and the phases coincide with each other, in addition to closing the switch 145 as in the first embodiment, the power converter 100 of the arm circuit 115 (1) Switching operation is stopped. Therefore, the configuration of the control unit 150 of the second embodiment is slightly different from the configuration of the control unit 150 of the first embodiment.

  Compared with the configuration of the control unit 150 according to the first embodiment illustrated in FIG. 2, the control unit 150 according to the second embodiment may include the switch 163 and the gate signal cutoff circuit 200. Different. Other configurations are the same.

  The gate signal cutoff circuit 200 provided in the control unit 150 of the second embodiment receives the SW excitation signal output from the synchronization / phase matching detection circuit 180 and stops switching of the switching elements of the arm circuit 115 (1). The gate signal cut-off circuit 200 cuts off the switching signal output from the converter drive circuit 166 when the SW excitation signal is output, and passes the switching signal when the SW excitation signal is not output.

[Operation of power converter]
<When input phase voltage and output voltage are not synchronized or in phase>
The operation of the power conversion apparatus 100 in this case is the same as the operation of the power conversion apparatus 100 according to the first embodiment because the gate signal cutoff circuit 200 passes the switching signal.

<When input phase voltage and output voltage are synchronized and in phase>
In this case, the synchronization / phase coincidence detection circuit 180 outputs a SW excitation signal. Therefore, the switching circuit 173 outputs a signal output from the PLL circuit 171 oscillator 172, the switch 145 (see FIG. 1) is closed by the SW excitation circuit 190, the gate signal cutoff circuit 200 includes the converter drive circuit 166 and the arm circuit 115. The switching signal output for (1) is cut off.

  Arm circuit 115 (2),..., Arm circuit 115 (n) performs a switching operation using a switching signal output from converter drive circuit 166. Only the arm circuit 115 (1) does not perform the switching operation.

  Therefore, when the input phase voltage and the output voltage are synchronized and in phase with each other, the arm circuit 115 (1) does not perform the switching operation, so that the current flows through the arm circuit 115 (1) as in the first embodiment. Absent. For this reason, the total loss (energization loss + switching loss) of the switching circuits 117 (11) and 117 (12) and the reactor 118 (1) becomes zero.

  Furthermore, in the case of the second embodiment, the gate signal cutoff circuit 200 blocks the switching signal for the switching circuits 117 (11) and 117 (12) of the arm circuit 115 (1). The switching loss of 117 (11) and 117 (12) is also zero. For this reason, the loss of the power converter device 100 of Embodiment 2 becomes smaller than the loss of the power converter device 100 of Embodiment 1.

  In the case of the second embodiment, similarly to the case of the first embodiment, the arm circuit 135 (1) of the inverter 130 plays the role of the arm circuit 115 (1) of the converter 110. That is, the arm circuit 135 (1) of the inverter 130 becomes a shared arm of the arm circuit 115 (1) of the converter 110 and the arm circuit 135 (1) of the inverter 130.

[Embodiment 3]
[Configuration of power converter]
The configuration of the power conversion device 300 according to the third embodiment is the same as the configuration of the power conversion device 100 according to the first embodiment except for the number and arrangement of switches.

  FIG. 7 is a schematic configuration diagram of a power conversion device 300 according to the third embodiment. The power conversion device 300 includes a converter 310, an inverter 330, and a control unit 350.

<Configuration of converter and inverter>
The converter 310 and the inverter 330 of the power converter according to the third embodiment are shown as blocks in FIG. The configurations of the converter 310 and the inverter 330 are the same as the configurations of the converter 110 and the inverter 130 of the power conversion device 100 according to the first embodiment shown in FIG.

  A smoothing capacitor 340 is connected between the converter 310 and the inverter 330. Between the AC input terminals IN (1), IN (2),..., IN (n) of the converter 310 and the AC output terminals OUT (1), OUT (2),. The switch group SWB constituting the bypass switch is connected. Specifically, the switch swb (1) is connected between the AC input terminal IN (1) of the converter 310 and the AC output terminal OUT (1) of the inverter 330, and the AC input terminal IN (2) and the AC output. A switch swb (2) is connected between the terminal OUT (2) and a switch swb (n) is connected between the AC input terminal IN (n) and the AC output terminal OUT (n).

  A switch group SWIN constituting an input switch is connected between the converter 310 and the AC input terminals IN (1), IN (2),..., IN (n). Specifically, the switch spin (1) is connected between the converter 310 and the AC input terminal IN (1), and the switch spin (2) is connected between the converter 310 and the AC input terminal IN (2). A switch swin (n) is connected between the converter 310 and the AC input terminal IN (n).

  A switch group SWOUT constituting an output switch is connected between the inverter 330 and the AC output terminals OUT (1), OUT (2),..., OUT (n). Specifically, the switch swout (1) is connected between the inverter 330 and the AC output terminal OUT (1), and the switch swout (2) is connected between the inverter 330 and the AC output terminal OUT (2). The switch swout (n) is connected between the inverter 330 and the AC output terminal OUT (n).

  The switch group SWB, the switch group SWIN, and the switch group SWOUT are provided for maintenance of the power converter 300. At the time of maintenance, all the switches in the switch group SWB are closed, and all the switches in the switch group SWIN and the switch group SWOUT are opened.

  Thus, AC input terminals IN (1), IN (2),..., IN (n) are directly connected to AC output terminals OUT (1), OUT (2),. Are disconnected from the AC input terminals IN (1), IN (2),..., IN (n), and the inverter 330 is disconnected from the AC output terminals OUT (1), OUT (2),. . Therefore, maintenance of the converter 310, the inverter 330, and the like can be performed while supplying power to the load from the AC input terminals IN (1), IN (2),..., IN (n).

  Operation of converter 310 and inverter 330, switch group SWB (switches swb (1) -swb (n)), switch group SWIN (switches swin (1) -swin (n)), switch group SWOUT (switches swout (1)) -Swout (n)) is controlled by the control unit 350.

<Configuration of control unit>
The power conversion device 300 according to the third embodiment uses the switch group SWB used at the time of maintenance, and when the input phase voltage and the output voltage are synchronized and in phase, the switching circuit of the converter 310 is the same as in the first embodiment. The energization loss of 117 (11) and 117 (12), and the reactor 118 (1) (see FIG. 1) is made almost zero.

  FIG. 8 is a block diagram of a control unit of the power conversion apparatus according to the third embodiment. Since the configuration of the control unit 350 of the power conversion device according to the third embodiment needs to open and close the maintenance switch group SWB, the switch group SWIN, and the switch group SWOUT, the configuration is compared with the configuration of the control unit 150 of the first embodiment. Slightly different.

  As shown in FIG. 8, the control unit 350 includes a converter control unit 360, an inverter control unit 370, a synchronization / phase matching detection circuit 380, an inverter / bypass selection circuit 385, a SWB excitation circuit 390, a SWIN excitation circuit 392, and a SWOUT excitation circuit. 394.

  Converter control unit 360 includes an input current amplitude command generation circuit 361, an input current reference sine wave generation circuit 362, a switch 363, a converter phase voltage modulation command generation circuit 364, a PWM signal generation circuit 365, and a converter drive circuit 366.

  The input current amplitude command generation circuit 361, the input current reference sine wave generation circuit 362, the switch 363, the converter phase voltage modulation command generation circuit 364, the PWM signal generation circuit 365, and the converter drive circuit 366 are the same as the input current amplitude command of the first embodiment. The generator circuit 161, the input current reference sine wave generation circuit 162, the switch 163, the converter phase voltage modulation command generation circuit 164, the PWM signal generation circuit 165, and the converter drive circuit 166 have the same functions.

  The inverter control unit 370 includes a PLL circuit 371, an oscillator 372, a switching circuit 373, an inverter voltage reference sine wave generation circuit 374, an inverter phase voltage modulation command generation circuit 375, a PWM signal generation circuit 376, and an inverter drive circuit 377.

  A PLL circuit 371, an oscillator 372, a switching circuit 373, an inverter voltage reference sine wave generation circuit 374, an inverter phase voltage modulation command generation circuit 375, a PWM signal generation circuit 376, and an inverter drive circuit 377 are the same as the PLL circuit 171 and the oscillator of the first embodiment 172, a switching circuit 173, an inverter voltage reference sine wave generation circuit 174, an inverter phase voltage modulation command generation circuit 175, a PWM signal generation circuit 176, and an inverter drive circuit 177.

  The synchronization / phase matching detection circuit 380 has the same function as the synchronization / phase matching detection circuit 180 of the first embodiment.

  The inverter / bypass selection circuit 385 selectively outputs a SW excitation signal to the OR circuit 386, the SWB excitation circuit 390, the SWIN excitation circuit 392, and the SWOUT excitation circuit 394. The SWB excitation circuit 390 is configured by swb (1) excitation circuit 390 (1) for opening / closing the switch swb (1),..., Swb (n) excitation circuit 390 (n) for opening / closing the switch swb (n) shown in FIG. ). The SWIN excitation circuit 392 includes a spin (1) excitation circuit 392 (1) that opens and closes the switch spin (1),..., And a spin (n) excitation circuit 392 (n) that opens and closes the switch spin (n). The SWOUT excitation circuit 394 includes a swout (1) excitation circuit 394 (1) that opens and closes the switch swout (1), and a swout (n) excitation circuit 392 (n) that opens and closes the switch swout (n).

  The inverter / bypass selection circuit 385 outputs a SW excitation signal only to the SWB excitation circuit 390 during maintenance. Therefore, during maintenance, the swb (1) excitation circuit 390 (1),..., Swb (n) excitation circuit 390 (n) closes the switch swb (1),..., Switch swb (n) via the OR circuit 386. . During maintenance, no SW excitation signal is output to the SWIN excitation circuit 392 and the SWOUT excitation circuit 394. swin (1),..., switch swin (n) and sout (1),..., switch sout (n) are open.

  On the other hand, the inverter / bypass selection circuit 385 does not output the SW excitation signal to the SWB excitation circuit 390 and outputs the SW excitation signal to the SWIN excitation circuit 392 and the SWOUT excitation circuit 394 when maintenance is not performed. Therefore, when the maintenance is not performed, the spin (1) excitation circuit 392 (1),..., The spin (n) excitation circuit 392 (n) closes the switch spin (1),. Excitation circuit 394 (1), ..., swout (n) Excitation circuit 394 (n) closes switch swout (1), ..., switch swout (n). swb (1),..., switch swb (n) is open.

  Summarizing the open / closed state of each switch group, the switch group SWIN (switches swin (1) -swin (n)) and the switch group SWOUT (switches sout (1) -swout (n)) during normal times when maintenance is not performed. Are closed, and all switches of the switch group SWB (switches swb (1) -swb (n)) are opened.

  On the other hand, at the time of maintenance, all the switches of the switch group SWIN (switches swin (1) -swin (n)) and switch group SWOUT (switches sout (1) -swout (n)) are opened, and the switch group SWB (switches All switches of swb (1) -swb (n)) are closed. Therefore, maintenance of converter 310 and inverter 330 can be performed while supplying power to the load.

[Operation of power converter]
[Operation during maintenance]
At the time of maintenance, since the inverter / bypass selection circuit 385 outputs the SW excitation signal only to the SWB excitation circuit 390, all the switches in the switch group SWB (switches swb (1) -swb (n)) are closed. Since no SW excitation signal is output to the SWIN excitation circuit 392 and the SWOUT excitation circuit 394, the switch group SWIN (switches swin (1) -swin (n)) and the switch group SWOUT (switches sout (1) -swout (n)) All switches in are opened.

  Therefore, the AC input terminals IN (1), IN (2),..., IN (n) are disconnected from the converter 310, and the AC output terminals OUT (1), OUT (2),. Is disconnected from the inverter 330. Since converter 310 and inverter 330 are in a non-live line state, maintenance is facilitated.

  Also, the AC input terminals IN (1), IN (2),..., IN (n) are directly connected to the AC output terminals OUT (1), OUT (2),. A load connected to the output terminals OUT (1), OUT (2),..., OUT (n) can be driven as it is.

[Operation when not during maintenance]
<When input phase voltage and output voltage are not synchronized or in phase>
When it is not during maintenance, the inverter / bypass selection circuit 385 does not output the SW excitation signal to the SWB excitation circuit 390. When the input phase voltage VIN (1) and the output voltage VOUT (1) are not synchronized or the phases are not matched, the synchronization / phase match detection circuit 380 does not output the SW excitation signal. On the other hand, a SW excitation signal is output to the SWIN excitation circuit 392 and the SWOUT excitation circuit 394.

  For this reason, not at the time of maintenance, and when the input phase voltage and the output voltage are not synchronized or in phase, all the switches of the switch group SWB (switches swb (1) -swb (n)) Will be opened. In addition, all the switches of the switch group SWIN (switches swin (1) -swin (n)) and the switch group SWOUT (switches sout (1) -swout (n)) are closed.

  Therefore, when the input phase voltage and the output voltage are not synchronized or in phase, the AC power input to converter 310 is converted to DC power of a predetermined voltage, and the DC power input to inverter 330 is The electric power is converted into AC power having a predetermined voltage. That is, converter 310 and inverter 330 operate normally.

<When input phase voltage and output voltage are synchronized and in phase>
When it is not during maintenance, the inverter / bypass selection circuit 385 does not output the SW excitation signal to the SWB excitation circuit 390. On the other hand, when the input phase voltage and the output voltage are synchronized and in phase, the synchronization / phase matching detection circuit 380 outputs the SW excitation signal. Therefore, the SW excitation signal is input to the swb (1) excitation circuit 390 (1) via the OR circuit 386, and only the switch swb (1) in the switch group SWB is closed. Further, a SW excitation signal is output to the SWIN excitation circuit 392 and the SWOUT excitation circuit 394.

  For this reason, when the input phase voltage and the output voltage are synchronized and in phase, not at the time of maintenance, only the switch swb (1) in the switch group SWB is closed and the switch group SWIN (switch swin ( 1) -swin (n)) and all switches in the switch group SWOUT (switches swout (1) -swout (n)) are closed.

  The switch 363 outputs a 0V input current reference sine wave by the SW excitation signal output from the synchronization / phase coincidence detection circuit 380, and the switch circuit 373 outputs a signal output from the oscillator 372.

  The operation of controlling the converter 310 using the 0 V input current reference sine wave and the operation of controlling the inverter 330 using the signal output from the oscillator 372 are the same as those of the control unit 150 of the first embodiment.

  Also in the case of the third embodiment, a current flows through the converter 310 and the inverter 330 in the same manner as the power conversion device 100 of the first embodiment (see FIGS. 4 and 5). Therefore, similarly to the power conversion device 100 of the first embodiment, since no current flows into the arm circuit of the converter 310, the energization loss of the switching element and the reactor of the arm circuit is almost zero.

  In the case of the third embodiment, the switch group SWB provided for maintenance is effectively utilized. Therefore, unlike the first and second embodiments, it is not necessary to provide a switch that opens and closes when the input phase voltage and the output voltage are synchronized and in phase.

[Embodiment 4]
[Configuration of power converter]
The configuration of the power conversion device 300 according to the fourth embodiment is the same as the configuration of the power conversion device 100 according to the second embodiment except for the number and arrangement of switches. The number and arrangement of switches are the same as those of the power conversion apparatus 300 according to the third embodiment.

<Configuration of converter and inverter>
Moreover, the structure of the converter 310 and the inverter 330 of the power converter device 300 which concerns on Embodiment 4 is the same as the structure of the power converter device 300 which concerns on Embodiment 3. FIG.

<Configuration of control unit>
The power conversion device 300 according to the fourth embodiment uses the switch group SWB used at the time of maintenance, and when the input phase voltage and the output voltage are synchronized and in phase, the switching circuit of the converter 310 is the same as in the second embodiment. The total loss (energization loss + switching loss) of 117 (11) and 117 (12) and reactor 118 (1) (see FIG. 1) is set to zero.

  FIG. 9 is a block diagram of a control unit of the power conversion apparatus according to the fourth embodiment. Compared with the configuration of the control unit 350 according to the third embodiment, the configuration of the control unit 350 of the power conversion device according to the fourth embodiment has no switching device 363 and has a gate signal cutoff circuit 400. Is different. Other configurations are the same.

  The gate signal cutoff circuit 400 included in the control unit 350 of the fourth embodiment receives the SW excitation signal output from the synchronization / phase matching detection circuit 380 and stops switching of the switching elements of the arm circuit of the converter 310. The gate signal cut-off circuit 400 cuts off the switching signal output from the converter drive circuit 366 when the SW excitation signal is output, and passes the switching signal when the SW excitation signal is not output.

[Operation of power converter]
[Operation during maintenance]
The operation at the time of maintenance is the same as that of the power conversion device 300 according to the third embodiment.

[Operation when not during maintenance]
<When input phase voltage and output voltage are not synchronized or in phase>
The operation is the same as that of the power conversion apparatus 300 according to the third embodiment when not in maintenance and when the input phase voltage and the output voltage are not synchronized or in phase.

<When input phase voltage and output voltage are synchronized and in phase>
If the input phase voltage and output voltage are synchronized and in phase, not during maintenance,
As in the third embodiment, only the switch swb (1) in the switch group SWB is closed, and the switch group SWIN (switches swin (1) -swin (n)) and the switch group SWOUT (switches swout (1) -swout). All switches in (n)) are closed.

  Further, the switching circuit 373 outputs a signal output from the oscillator 372 by the SW excitation signal output from the synchronization / phase matching detection circuit 380, and the gate signal cut-off circuit 400 is the arm circuit 115 (1) of the converter 310 (FIG. 1). The switching of the switching element of (see) is stopped.

  In the case of the fourth embodiment, since the gate signal cutoff circuit 400 blocks the switching signal sent to the switching circuit of the arm circuit of the converter 310, the loss of the power conversion device 300 according to the fourth embodiment is the same as that of the third embodiment. It becomes smaller than the loss of the power converter device 300 concerned.

  As described above, in the power conversion devices according to the first and third embodiments, the current of the fundamental wave of the commercial frequency does not need to flow through the circuit (switching element and reactor) for one phase of the converter. Loss occurring in the circuit can be reduced.

  In the power converters according to the second and fourth embodiments, since no current flows in the circuit (switching element and reactor) for one phase of the converter, the loss generated in the circuit for one phase of the converter and the converter Loss caused by the reactor can be reduced to zero.

  Furthermore, in the power conversion devices according to the first to fourth embodiments, the current flowing through one arm of the inverter serving as the shared arm is a current having a phase opposite to the input current when the power factor of the load of the inverter is 1, It cancels out and becomes a small current. For this reason, the loss of one arm of the inverter serving as the shared arm is further reduced.

  In the power converters according to the third and fourth embodiments, the switch group SWB provided for maintenance is effectively used, so that the input phase voltage and the output voltage are synchronized with each other as in the first and second embodiments. There is no need to provide a special switch that opens and closes when they match.

  The preferred embodiments of the present invention have been described above, but these are examples for explaining the present invention, and the scope of the present invention is not intended to be limited to these embodiments. The present invention can be implemented in various modes different from the above-described embodiments without departing from the gist thereof.

100, 300 power converter,
110, 310 converter,
115 (1), 115 (2),... 115 (n) arm circuit,
117 (11), 117 (12), 117 (21), 117 (22), ... 117 (n1), 117 (n2) switching circuits 118 (1), 118 (2), ..., 118 (n) reactors 130, 330 inverter,
135 (1), 135 (2),... 135 (n) arm circuit,
137 (11), 137 (12), 137 (21), 137 (22),... 137 (n1), 137 (n2) Switching circuit 138 (1), 138 (2),..., 138 (n) reactor 139 (1), 139 (2), ..., 139 (n) capacitor 140, 340 smoothing capacitor,
145 switch,
150, 350 control unit,
160, 360 converter control unit,
161, 361 input current amplitude command generation circuit,
162, 362 input current reference sine wave generation circuit,
163, 363 switching device,
164, 364 converter phase voltage modulation command generation circuit,
165, 176, 365, 376, PWM signal generation circuit,
166, 366 converter drive circuit,
177, 377 inverter drive circuit,
170, 370 Inverter control unit,
171, 371 PLL circuit,
172, 372 oscillator,
173, 373 switching circuit,
174, 374 inverter voltage reference sine wave generation circuit,
175, 375 inverter phase voltage modulation command generation circuit,
180, 380 synchronization / phase coincidence detection circuit,
190 SW excitation circuit,
200, 400 Gate signal cutoff circuit,
385 Inverter / bypass selection circuit,
386 OR circuit,
390 SWB excitation circuit,
392 SWIN excitation circuit,
394 SWOUT excitation circuit.

Claims (13)

A converter that converts AC power input from the AC input terminal into DC power;
An inverter that converts DC power input from the converter into AC power and outputs it from an AC output terminal;
One switch for connecting the same phase of the AC input terminal and the AC output terminal,
The converter and the inverter have a plurality of arm circuits connected in parallel, the arm circuits have at least two or more switching circuits connected in series, and the switching circuits are connected in parallel. A rectifying element and a switching element;
When the synchronization and phase of the AC voltage at the AC input terminal and the AC voltage at the AC output terminal match, the switch is closed so that the current flowing through the arm circuit connected to the switch of the converter becomes zero. The power converter characterized by controlling to. A converter that converts AC power input from the AC input terminal into DC power;
An inverter that converts DC power input from the converter into AC power and outputs it from an AC output terminal;
One switch for connecting the same phase of the AC input terminal and the AC output terminal,
The converter and the inverter have a plurality of arm circuits connected in parallel, the arm circuits have at least two or more switching circuits connected in series, and the switching circuits are connected in parallel. A rectifying element and a switching element;
When the synchronization and phase of the AC voltage at the AC input terminal and the AC voltage at the AC output terminal match, the switch is closed, and the switching element of the switching circuit of the arm circuit that connects the switch of the converter A power converter that stops switching.   The power conversion device according to claim 1, further comprising a synchronization / phase matching detection unit that detects synchronization and phase matching between the AC voltage at the AC input terminal and the AC voltage at the AC output terminal.   In order to reduce the current flowing through one arm circuit of the converter to 0, the switching circuit of the arm circuit is configured so that the current flowing through the one arm circuit becomes 0 using an input current reference sine wave of 0V. The power conversion device according to claim 1, wherein the switching of the switching element is controlled.   The power converter according to any one of claims 1 to 4, wherein a reactor functioning as a filter is connected between the converter and the AC input terminal.   The power converter according to any one of claims 1 to 4, wherein a reactor and a capacitor that function as a filter are connected between the inverter and the AC output terminal. A converter that converts AC power input from the AC input terminal into DC power;
An inverter that converts DC power input from the converter into AC power and outputs it from an AC output terminal;
A switch group provided between the AC input terminal and the converter, between the AC output terminal and the inverter, between the AC input terminal and the AC output terminal, and
The converter and the inverter have a plurality of arm circuits connected in parallel, the arm circuits have at least two or more switching circuits connected in series, and the switching circuits are connected in parallel. A rectifying element and a switching element;
When not during maintenance, close all switch groups provided between the AC input terminal and the converter, between the AC output terminal and the inverter,
One of the switch groups provided between the AC input terminal and the AC output terminal when the synchronization and phase of the AC voltage of the AC input terminal and the AC voltage of the AC output terminal coincide with each other when maintenance is not performed. Close only one switch,
Controlling power so that an electric current flowing through an arm circuit connected to a closed switch of a group of switches provided between the AC input terminal and the AC output terminal of the converter is zero. apparatus. A converter that converts AC power input from the AC input terminal into DC power;
An inverter that converts DC power input from the converter into AC power and outputs it from an AC output terminal;
A switch group provided between the AC input terminal and the converter, between the AC output terminal and the inverter, between the AC input terminal and the AC output terminal, and
The converter and the inverter have a plurality of arm circuits connected in parallel, the arm circuits have at least two or more switching circuits connected in series, and the switching circuits are connected in parallel. A rectifying element and a switching element;
When not during maintenance, close all switch groups provided between the AC input terminal and the converter, between the AC output terminal and the inverter,
One of the switch groups provided between the AC input terminal and the AC output terminal when the synchronization and phase of the AC voltage of the AC input terminal and the AC voltage of the AC output terminal coincide with each other when maintenance is not performed. Close only one switch,
Electric power for stopping switching of a switching element included in a switching circuit of an arm circuit connected to a closed switch of a switch group provided between the AC input terminal and the AC output terminal of the converter Conversion device.   9. The power conversion device according to claim 7, further comprising a synchronization / phase matching detection unit that detects synchronization and phase matching between the AC voltage of the AC input terminal and the AC voltage of the AC output terminal.   In order to reduce the current flowing through one arm circuit of the converter to 0, the switching circuit of the arm circuit is configured so that the current flowing through the one arm circuit becomes 0 using an input current reference sine wave of 0V. The power conversion device according to claim 7, wherein switching of the switching element having the control is controlled.   The power converter according to any one of claims 7 to 10, wherein a reactor that functions as a filter is connected between the converter and the AC input terminal.   The power converter according to any one of claims 7 to 10, wherein a reactor and a capacitor functioning as a filter are connected between the inverter and the AC output terminal.   During maintenance, all switch groups provided between the AC input terminal and the converter, between the AC output terminal and the inverter are opened, and a switch group provided between the AC input terminal and the AC output terminal. The power conversion device according to any one of claims 8 to 12, characterized in that all are closed.