JP5043585B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device that includes a circuit that improves an input power factor and converts AC power into DC power.

  The conventional power converter device connects a reactor in series to each phase of three-phase alternating current. These lines are connected to the input side of a bridge rectifier circuit composed of six diodes. In the bridge rectifier circuit, FETs are connected in parallel to the three diodes. The FETs are simultaneously turned on / off by a high-frequency switching signal from the control circuit, and the output adjustment is performed by time ratio control (see, for example, Patent Document 1).

JP-A-8-126330

  In such a power converter, in order to control the current from the AC power source, the AC voltage is switched at a high frequency by the semiconductor switch, so that a great deal of loss and noise occur. If the switching frequency is lowered to avoid this problem, a large current-limiting reactor is required to obtain a good input power factor.

  The present invention has been made to solve the above-described problems, and performs input current control for improving the input power factor and voltage control of the output stage to convert AC power into DC power. An object of the present invention is to reduce power loss and noise in a power conversion device, and to promote downsizing of the device configuration by eliminating a large current limiting circuit.

The power conversion device according to the present invention is configured by connecting one or more AC sides of a single-phase inverter composed of a plurality of semiconductor switch elements and a DC voltage source in series, and the AC side is connected to each of three-phase AC input power sources. Each phase inverter circuit that is connected in series to each phase AC input line and superimposes the sum of the outputs of each of the above single phase inverters on each phase AC input, and a smoothing that is arranged downstream of each phase inverter circuit and smoothes the output Capacitors, rectifier diodes for each phase with the anode side connected to each phase AC output line at the subsequent stage of each phase inverter circuit and the cathode side connected to the positive electrode of the smoothing capacitor, and each stage at the subsequent stage of each phase inverter circuit A short-circuit switch for each phase, one end of which is connected to the phase AC output line and the other end of which is connected to the negative electrode of the smoothing capacitor.
Then, the shorting switch of the phase is turned on in a predetermined phase range including the zero-cross phase of each phase input voltage from the AC input power source, and the voltage of the smoothing capacitor follows the target voltage and the AC input power source The output control of each phase inverter circuit is performed using the current command of each phase so as to improve the input power factor.

  According to the present invention, the short-circuit switch does not require high-frequency switching, and the inverter circuit that improves the input power factor and controls the voltage of the output stage can make the voltage handled by switching relatively small. For this reason, switching loss and noise can be reduced without requiring a large current limiting circuit, and a power conversion device in which reduction of power loss and noise and miniaturization of the device configuration are promoted can be realized.

Embodiment 1 FIG.
Hereinafter, a power converter according to Embodiment 1 of the present invention will be described. FIG. 1 is a schematic configuration diagram of a power conversion device according to Embodiment 1 of the present invention.
As shown in FIG. 1, each phase AC input line from a three-phase AC voltage source 1 (hereinafter simply referred to as AC power source 1) as an AC input power source is connected to reactors 2a to 2c of each phase as a current limiting circuit. Then, the AC side of each phase inverter circuit 100a to 100c (hereinafter simply referred to as inverter circuits 100a to 100c) configured by a single phase inverter is connected in series at the subsequent stage. Single-phase inverters constituting each of the inverter circuits 100a to 100c are composed of semiconductor switch elements 3a to 3d and a DC voltage source 4. Here, as the semiconductor switch elements 3a to 3d, an IGBT (Insulated Gate Bipolar Transistor) in which diodes are connected in antiparallel, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) in which a diode is built in between source and drain, or the like is used. In addition, you may connect the reactors 2a-2c of each phase in series with the back | latter stage of inverter circuits 100a-100c.

In addition, short-circuit switches 5a to 5c for each phase made of semiconductor switch elements and rectifier diodes 6a to 6c for each phase are connected to respective phase AC output lines at the subsequent stage of each inverter circuit 100a to 100c. The rectifier diodes 6 a to 6 c are connected at the cathode side to the positive electrode of the smoothing capacitor 7 for output, and the other ends of the short-circuit switches 5 a to 5 c are connected to the negative electrode of the smoothing capacitor 7. In this case, three sets of series circuits in which short-circuit switches 5a to 5c and rectifier diodes 6a to 6c are connected in series are connected between both terminals of the output smoothing capacitor 7, and each midpoint of the three sets of series circuits is connected. Is connected to each phase AC output line in the subsequent stage of each of the inverter circuits 100a to 100c.
Each of the short-circuit switches 5a to 5c is not limited to a semiconductor switch element, and may be a mechanical switch or the like, but the diodes 8a to 8c are connected in antiparallel.

The operation of the power conversion device configured as described above will be described based on the waveform of each part shown in FIG. 2 for one of the three phases, for example, the A phase. The other two phases (B phase and C phase) are also shifted in phase by 2π / 3, but operate similarly.
When the phase voltage input from the AC power supply 1 is the voltage Vin and the phase current is the current Iin, the waveform is as shown in FIG. Vdc is a DC voltage of the smoothing capacitor 7 controlled to a constant target voltage Vdc ^* . In this case, the peak voltage of the voltage Vin is higher than the DC voltage Vdc of the smoothing capacitor 7.
The A-phase inverter circuit 100a controls and outputs the current Iin by PWM control so that the A-phase input power factor from the AC power supply 1 is approximately 1, and superimposes the generated voltage on the AC side on the voltage Vin.

For example, when the voltage Vin and the current Iin are positive, the current in the inverter circuit 100a flows as follows. When all of the semiconductor switch elements 3a to 3d are off, the DC voltage source 4 is charged through the diode of the semiconductor switch element 3b and output through the diode of the semiconductor switch element 3c. When only the semiconductor switch element 3a is turned on, the current is output through the semiconductor switch element 3a and the diode of the semiconductor switch element 3c. Similarly, when only the semiconductor switch element 3d is turned on, a current is output through the diode of the semiconductor switch element 3b and the semiconductor switch element 3d. When the semiconductor switch elements 3a and 3d are simultaneously turned on, the DC voltage source 4 is discharged through the semiconductor switch element 3a and output through the semiconductor switch element 3d.
When the voltage Vin and the current Iin are negative, the semiconductor switch elements 3a to 3d are all turned off to charge the DC voltage source 4, and only the semiconductor switch element 3b or the semiconductor switch element 3c is turned on to turn on the DC voltage source 4 And the semiconductor switch elements 3b and 3c are simultaneously turned on to discharge the DC voltage source 4.
The semiconductor switch elements 3a to 3d are controlled by such a combination of controls, and the inverter circuit 100a is PWM-controlled.

The phase A input voltage phase from the AC power source 1 is θ, and the phase when the phase A voltage Vin equals the target voltage Vdc ^* of the smoothing capacitor 7 is θ = θ ₂ (0 <θ ₂ <π / 2). From the phase θ = 0 to the predetermined phase θ ₁ where 0 <θ ₁ <θ ₂ , the shorting switch 5a connected to the subsequent stage of the inverter circuit 100a is turned on. In this case, as shown in FIG. 3, the A-phase current is expressed as follows: AC power source 1 → reactor 2a → inverter circuit 100a → shorting switch 5a → diode 8c (or diode 8b) → inverter circuit 100c (or inverter circuit 100b) → Reactor 2c (or reactor 2b) flows through the path of AC power source 1. At this time, the A-phase current does not flow through the rectifier diode 6a and the smoothing capacitor 7 in the output stage. For example, the inverter circuit 100a has a polarity opposite to that of the voltage Vin by combining PWM when the semiconductor switch elements 3a to 3d are all turned off and when only the semiconductor switch element 3a (or the semiconductor switch element 3d) is turned on. While generating substantially the same voltage, the current Iin is controlled and output so that the input power factor becomes approximately 1, and during this time, the DC voltage source 4 of the inverter circuit 100a is charged with energy.

Then, when the phase theta = theta _1, when turning off the short-circuiting switch 5a, as shown in FIG. 4, the current of the A phase, AC power source 1 → reactor 2a → inverter circuit 100a → rectifying diode 6a → the smoothing capacitor 7 → Diode 8c (or diode 8b) → Inverter circuit 100c (or inverter circuit 100b) → Reactor 2c (or reactor 2b) → AC power supply 1
When the phase θ is θ ₁ ≦ θ ≦ θ ₂ , the inverter circuit 100a is controlled by PWM control, for example, when the semiconductor switch elements 3a and 3d are turned on at the same time and only the semiconductor switch element 3a (or the semiconductor switch element 3d). Output in combination with the case of ON. At this time, the current Iin is controlled so that the input power factor becomes approximately 1 while generating a voltage substantially equal to Vdc ^* −Vin so that the DC voltage Vdc of the smoothing capacitor 7 can be maintained at the target voltage Vdc ^*. Output. During this time, the polarity of the voltage generated by the inverter circuit 100a is equal to the polarity of the current Iin, so that the DC voltage source 4 of the inverter circuit 100a is discharged.

Then, when the voltage Vin at the phase theta = theta ₂ becomes equal to the DC voltage Vdc ^* of the smoothing capacitor 7, the short-circuiting switch 5a is to keep it off, change the operation of the inverter circuit 100a.
That is, when the phase θ is θ ₂ ≦ θ ≦ π / 2, the A-phase current is: AC power source 1 → reactor 2a → inverter circuit 100a → rectifier diode 6a → smoothing capacitor 7 → diode 8c (or diode 8b) → It flows through the path of the inverter circuit 100c (or the inverter circuit 100b) → the reactor 2c (or the reactor 2b) → the AC power source 1. Further, the inverter circuit 100a outputs, for example, a combination of a case where all of the semiconductor switch elements 3a to 3d are turned off and a case where only the semiconductor switch element 3a (or the semiconductor switch element 3d) is turned on by PWM control. At this time, the target voltage Vdc ^* ≦ voltage Vin of the smoothing capacitor 7 is satisfied, and the inverter circuit 100a sets a voltage approximately equal to Vin−Vdc ^* so that the DC voltage Vdc of the smoothing capacitor 7 can be maintained at the target voltage Vdc ^*. The current Iin is controlled and output so that the input power factor becomes approximately 1 while being generated in the opposite polarity to the polarity of. During this time, the polarity of the voltage generated by the inverter circuit 100a and the polarity of the current Iin are reversed, so that the DC voltage source 4 of the inverter circuit 100a is charged.

As shown in FIG. 2, in the phase period of π / 2 ≦ θ ≦ π, the operation is symmetrical with the phase period of 0 ≦ θ ≦ π / 2. In the phase period of π ≦ θ ≦ 2π, the voltage Vin and the current Iin are negative, and the A phase current does not flow through the rectifier diode 6a but flows through the shorting switch 5a or the diode 8a. Also in this case, similarly to the phase period of 0 ≦ θ ≦ π, the inverter circuit 100a switches between charging / discharging of the DC voltage source 4 so that the DC voltage Vdc of the smoothing capacitor 7 can be maintained at the target voltage Vdc ^* . Further, the current Iin is controlled and output so that the input power factor is approximately 1.
In this way, the short-circuit switch 5a is switched with the zero cross phase (θ = 0, π) ± θ ₁ of the phase θ of the A phase input voltage from the AC power supply 1 as a specific phase, and the phase range of ± θ ₁ from the zero cross phase Only in the following (hereinafter referred to as short-circuit phase range 9), the short-circuit switch 5a is turned on. At this time, the inverter circuit 100a generates and outputs a voltage substantially equal to the reverse polarity of the voltage Vin, controls and outputs the current Iin so that the input power factor is approximately 1, and the DC voltage source 4 is charged. In a phase other than the short-circuit phase range 9, the inverter circuit 100a maintains the DC voltage Vdc of the smoothing capacitor 7 at the target voltage Vdc ^* and controls the current Iin so that the input power factor is approximately 1. Output. At this time, when the absolute value of the voltage Vin is equal to or lower than the target voltage Vdc ^* of the smoothing capacitor 7, the DC voltage source 4 is discharged. When the absolute value of the voltage Vin is equal to or higher than the target voltage Vdc ^* , the DC voltage source 4 is charged. Is done.

When θ ₁ is increased, the energy charged in the DC voltage source 4 is increased, and at the time of subsequent discharge, the generated voltage can be superimposed on the voltage Vin in the voltage region having a high absolute value, and the discharged energy can be increased. For this reason, the DC voltage Vdc (target voltage Vdc ^* ) of the smoothing capacitor 7 can be increased.
In the phase period of 0 ≦ θ ≦ π / 2, the DC voltage source 4 of the inverter circuit 100a is charged in the period of 0 ≦ θ ≦ θ ₁ and θ ₂ ≦ θ ≦ π / 2, as described above, and θ ₁ It is discharged at ≦ θ ≦ θ ₂ periods. Assuming that the charge / discharge energy of the DC voltage source 4 of the inverter circuit 100a is equal, the following formula is established. However, Vp is the peak voltage of the voltage Vin, and Ip is the peak current of the current Iin.

Here, if Vin = Vp sinθ and Iin = Ip sinθ,
Vdc ^* = Vp · π / (4cosθ ₁ )
It becomes. As described above, the target voltage Vdc ^* of the smoothing capacitor 7 is determined by θ ₁ that determines the short-circuit phase range 9, that is, can be controlled by changing θ ₁ . The DC voltage Vdc of the smoothing capacitor 7 is controlled so as to follow the target voltage Vdc ^* .

Further, when the voltage of the DC voltage source 4 of the inverter circuit 100a is Vsub, the inverter circuit 100a in each phase range of 0 ≦ θ ≦ θ ₁ , θ ₁ ≦ θ ≦ θ ₂ , θ ₂ ≦ θ ≦ π / 2. By setting the voltage Vsub to be greater than or equal to the desired generated voltage, the inverter circuit 100a can perform the desired control described above with high reliability. That is,
By setting the voltage Vsub to satisfy the three conditions of Vp sinθ ₁ ≦ Vsub, (Vdc ^* −Vp sinθ ₁ ) ≦ Vsub, (Vp−Vdc ^* ) ≦ Vsub, the DC voltage Vdc of the smoothing capacitor 7 becomes the target voltage. It is maintained in Vdc ^*, and the control of the inverter circuit 100a for controlling the current Iin as the input power factor becomes approximate 1 is performed reliably in all phases of the AC power supply a phase. The voltage Vsub of the DC voltage source 4 is set to be equal to or lower than the Vin peak voltage Vp.

As described above, the inverter circuits 100a to 100c of each phase maintain the DC voltage Vdc of the smoothing capacitor 7 at the target voltage Vdc ^* , and the current Iin of each phase so that the input power factor of each phase becomes approximately 1. To control. Details of the control of the inverter circuits 100a to 100c will be described below.
Each inverter circuit 100a-100c is controlled by a control block as shown in FIG. First, the PI-controlled output 11 is calculated using the difference between the DC voltage Vdc of the smoothing capacitor 7 at the output stage and the target voltage Vdc ^* as a feedback amount. Further, in order to keep the voltages Vsub-a, Vsub-b and Vsub-c of the DC voltage source 4 of each inverter circuit 100a to 100c constant, the voltages Vsub-a, Vsub-b and Vsub-c and their target voltages are maintained. Differences from Vsub ^* are obtained, and the outputs 11a to 11c subjected to PI control are calculated using the difference as a feedback amount. Then, the amplitude target value 12 of the current Iin is determined from the sum of the outputs 11a to 11c and the output 11. Based on the amplitude target value 12, a sine wave current command Iin ^* (Iin-a ^* , Iin-b ^* , Iin-b ^* ) synchronized with the voltage Vin (Vin-a, Vin-b, Vin-c) of each phase. Iin-c ^* ) is generated.

Next, the output of each phase is PI controlled using the difference between the current commands Iin-a ^* , Iin-b ^* , Iin-c ^* and the detected currents Iin-a, Iin-b, Iin-c as feedback amounts Are the voltage commands 13a to 13c of the respective phases that are the target values of the voltages generated by the inverter circuits 100a to 100c. At this time, the feedforward correction voltages ΔVa, ΔVb, ΔVc synchronized at the time of switching on / off of the short-circuit switches 5a-5c in the subsequent stages of the inverter circuits 100a-100c are added to correct the voltage commands 13a-13c for each phase. . Then, each phase of the inverter circuits 100a to 100c is controlled by PWM control using each phase voltage command 14a to 14c after correction (voltage command 13a to 13c before correction except when the shorting switches 5a to 5c are switched on / off). Drive signals 15a to 15c to the semiconductor switch elements 3a to 3d are generated, and the inverter circuits 100a to 100c are operated.

In a specific phase of zero cross phase (θ = 0, π) ± θ ₁ of voltage Vin that is an input voltage of each phase from AC power supply 1, short-circuit switches 5a to 5c connected to subsequent stages of inverter circuits 100a to 100c of the phase. Switch 5c on / off. When each of the inverter circuits 100a to 100c switches the short-circuit switches 5a to 5c connected to the subsequent stage from on to off, the inverter circuit 100a to 100c switches from the control for charging the DC voltage source 4 to the control for discharging, and from the off to on. Is switched from the control for discharging the DC voltage source 4 to the control for charging. As described above, by adding the feedforward correction voltages ΔVa to ΔVc synchronized when the shorting switches 5a to 5c are switched on and off to correct the voltage commands 13a to 13c, the control can be performed for the response time of the feedback control. You can prevent delays. The feedforward correction voltages ΔVa to ΔVc have the same polarity as the input voltage Vin of each phase when the shorting switches 5a to 5c are turned off, and the shorting switches 5a to 5c are turned off to on. When doing so, the voltage has a reverse polarity.

In this embodiment, the smoothing capacitor 7 is controlled by controlling the inverter circuits 100a to 100c of each phase by using the current commands Iin-a ^* , Iin-b ^* , and Iin-c ^* of each phase as described above. Control is performed so that the input power factor from the AC power source 1 is improved by causing the DC voltage Vdc to follow the target voltage Vdc ^* . The short-circuit switches 5a to 5c do not require high-frequency switching, and the inverter circuits 100a to 100c that improve the input power factor and control the DC voltage Vdc of the output stage are used to control the voltage handled by switching at the peak of each phase of the AC power supply 1. It can be significantly lower than the voltage. For this reason, switching loss and noise can be reduced without requiring large reactors 2a to 2c.

In addition, when the shorting switches 5a to 5c are in the on state, the inverter circuit 100a to 100c has a high voltage because the DC voltage source 4 of the inverter circuits 100a to 100c can be charged without outputting a voltage from the phase to the smoothing capacitor 7. The phase current can be passed through the AC power source 1 without generating the electric power, and the charged energy can be used for discharging the smoothing capacitor 7. For this reason, the voltage handled by switching can be further reduced, and higher efficiency and lower noise can be further promoted.
In this case, reactors 2a to 2c do not store energy, but operate as a current-limiting circuit that limits current, and the reliability of current control is improved.
Further, by setting the voltage Vsub of the DC voltage source 4 that is the DC voltage of the inverter circuits 100a to 100c to be equal to or lower than the peak voltage Vp of the voltage Vin, the above-described effects of high efficiency and low noise can be reliably obtained.

Further, since the short-circuit switches 5a to 5c are operated only in a specific phase of the voltage Vin of each phase, the power conversion device can be stably controlled and there is almost no loss due to switching. Since the zero cross phase (θ = 0, π) only at short phase range 9 ± theta _1, does not output voltage to the smoothing capacitor 7 from the phase shorting switch 5a~5c an on state, the absolute value of the voltage Vin Therefore, it is not necessary to output to the smoothing capacitor 7 in a low region, the DC voltage of each of the inverter circuits 100a to 100c can be configured low, and the effects of high efficiency and low noise can be obtained with certainty.
Further, since the target voltage Vdc ^* of the smoothing capacitor 7 can be controlled by θ _{1 in} the short circuit phase range 9, the target voltage Vdc ^* can be easily controlled, and the degree of freedom in design and control is improved.

In addition, when the short-circuit switches 5a to 5c are switched on / off, the inverter circuits 100a to 100c are controlled to switch the charging / discharging operation of the DC voltage source 4 using feedforward control. High speed control can be realized by preventing delay of control by the response time.
In addition, since the current command is changed so that the voltage Vsub of the DC voltage source 4 is kept constant, the power converter can be controlled stably. In addition, charging / discharging of the DC voltage source 4 can be balanced, and supply of DC power from the outside is unnecessary, and the apparatus configuration is simplified.
Note that voltage control of the DC voltage source 4 may be performed from the outside, and in that case, in the output control of the inverter circuits 100a to 100c, it is not necessary to perform control to keep the voltage Vsub constant.

In the above embodiment, the peak voltage of the voltage Vin is higher than the DC voltage Vdc of the smoothing capacitor 7, but may be lower. In that case, there is no operation in the above-described phase range of θ ₂ ≦ θ ≦ π / 2, the DC voltage source 4 is charged when 0 ≦ θ ≦ θ ₁ , and the DC voltage source 4 is charged when θ ₁ ≦ θ ≦ π / 2. Operates to discharge.
It is also possible to always turn off the short-circuit switches 5a to 5c by setting θ ₁ = 0. In this case, the DC voltage source 4 is discharged when 0 ≦ θ ≦ θ ₂ , and θ ₂ ≦ θ ≦ π / 2. The DC voltage source 4 operates to charge.

In the above embodiment, the short-circuit switches 5a to 5c are turned on only in the short-circuit phase range 9 of ± 0 ₁ from the zero-cross phase (θ = 0, π) of the voltage Vin of each phase. Is negative, the short-circuit switches 5a to 5c may be off, and current flows through the diodes 8a to 8c connected in reverse parallel to the short-circuit switches 5a to 5c. That is, the phase range of 0 ≦ θ ≦ θ ₁ and (π−θ ₁ ) ≦ θ ≦ π may be set as a short-circuit phase range, and the short-circuit switches 5a to 5c may be turned on only in this short-circuit phase range. In this case, the short-circuit switches 5a to 5c are switched even in the zero cross phase, but the above-described feedforward control for correcting the voltage command at the time of on / off switching is not performed in the zero cross phase (θ = 0, π).

In the control of each of the inverter circuits 100a to 100c in the above embodiment, one amplitude target value 12 of the current Iin is determined and the current command Iin ^* for each phase is generated. The amplitude target value may be determined. In this case, the DC voltage Vdc of the smoothing capacitor 7 is applied to the outputs 11a to 11c obtained by PI control of the difference between the voltages Vsub-a to Vsub-c of the DC voltage source 4 of the inverter circuits 100a to 100c and the target voltage Vsub ^*. And the output 11 obtained by PI control of the difference between the target voltage Vdc ^* and the target voltage Vdc ^* are added to determine the amplitude target value of the current Iin for each phase. As a result, the DC voltage of each of the inverter circuits 100a to 100c can be controlled to the target voltage Vsub ^* with higher reliability.

Moreover, in the said embodiment, although each inverter circuit 100a-100c showed what was comprised by one single phase inverter, as shown in FIG. 6, the alternating current side of several single phase inverter 10a, 10b is shown. May be connected in series to form inverter circuits 200a to 200c for each phase. In this case, the sum of the outputs of the single-phase inverters 10a and 10b becomes the output of the inverter circuits 200a to 200c. In order to improve the input power factor from the AC power source 1. Then, the generated voltage on the AC side is superimposed on the voltage Vin of each phase.
In this case, the inverter circuits 200a to 200c may output by gradation control that generates a stepped voltage waveform by the sum of the outputs of the plurality of single-phase inverters, or a specific single unit among the plurality of single-phase inverters. Only the phase inverter may be PWM controlled.

It is a block diagram of the power converter device by Embodiment 1 of this invention. It is a wave form diagram of each part explaining operation | movement of the power converter device by Embodiment 1 of this invention. It is a figure explaining operation | movement of the power converter device by Embodiment 1 of this invention. It is a figure explaining operation | movement of the power converter device by Embodiment 1 of this invention. It is a control block diagram which shows control of the inverter circuit by Embodiment 1 of this invention. It is a block diagram of the power converter device by another example of Embodiment 1 of this invention.

Explanation of symbols

1 AC power source as AC input power source, 2a-2c Reactor as current limiting circuit,
3a to 3d semiconductor switch element, 4 DC voltage source, 5a to 5c short-circuit switch,
6a-6c rectifier diode, 7 smoothing capacitor, 8a-8c diode,
9 Short-circuit phase range, 10a, 10b single-phase inverter,
100a to 100c each phase inverter circuit (single phase inverter),
200a to 200c Inverter circuit for each phase, Iin-a ^{* to} Iin-c ^* current command,
ΔVa to ΔVc Feedforward correction voltage.

Claims (8)

The AC side of a single-phase inverter composed of a plurality of semiconductor switch elements and a DC voltage source is connected in series with one or more, and the AC side is connected in series to each phase AC input line from a three-phase AC input power source. Each phase inverter circuit that superimposes the sum of the outputs of each single phase inverter on each phase AC input;
A smoothing capacitor that is arranged downstream of each phase inverter circuit and smoothes the output;
A rectifier diode of each phase in which the anode side is connected to each phase AC output line in the subsequent stage of each phase inverter circuit, and the cathode side is connected to the positive electrode of the smoothing capacitor;
A short-circuit switch for each phase, one end of which is connected to each phase AC output line of the subsequent stage of each phase inverter circuit, and the other end is connected to the negative electrode of the smoothing capacitor;
In the predetermined phase range including the zero cross phase of each phase input voltage from the AC input power supply, the shorting switch of the phase is turned on,
Electric power characterized by controlling the output of each phase inverter circuit using a current command for each phase so that the voltage of the smoothing capacitor follows the target voltage and improves the input power factor from the AC input power source Conversion device. The power conversion device according to claim 1, wherein a diode is connected in reverse parallel to the short-circuit switch of each phase. 3. The power conversion device according to claim 1, wherein the phase for turning on / off the short-circuit switch of each phase is a specific phase of each phase input voltage from the AC input power supply. 4. 4. The power converter according to claim 3, wherein the target voltage of the smoothing capacitor is adjusted by changing the specific phase for turning on / off the short-circuit switch of each phase. 5. During on / off switching of the phase of the short-circuiting switch, any one of claims 1 to 4 is the phase inverter circuit of the phase being controlled to switch the charge / discharge operation of the DC power The power conversion device according to item 1. The power conversion device according to any one of claims 1 to 5 , wherein a current limiting circuit is connected in series to the AC side of each phase inverter circuit. As the DC voltage of the phase inverter circuit becomes a predetermined value, any one of claim 1 to 6, by changing the current command of the respective phases and outputs controlling the phase inverter circuit The power converter device described in 1. DC voltage of the phase inverter circuit, a power converter according to any one of claims 1 to 7, characterized in that set lower than the peak value of each phase input voltage from the AC input power supply.

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