JP5523499B2 - Power converter - Google Patents

Description

  The present invention relates to a power converter that obtains a desired DC voltage by superimposing an AC output of a single-phase inverter on a power supply output.

  In the conventional power converter, the output from the first terminal of the AC power supply is connected to the reactor, and the AC side of the inverter circuit configured by a single-phase inverter is connected in series at the subsequent stage. The single-phase inverter in the inverter circuit includes a semiconductor switch element and a DC voltage source. Further, the first and second series circuits constituting the inverter by connecting the shorting switch and the rectifier diode in series are connected in parallel and connected between both terminals of the smoothing capacitor of the output stage. The midpoint of the first series circuit is connected to the AC output line at the subsequent stage of the inverter circuit, and the midpoint of the second series circuit is connected to the second terminal of the AC power supply.

  Then, the current is controlled by PWM control so that the DC voltage of the smoothing capacitor can be maintained at a constant target voltage, and the input power factor from the AC power source is approximately 1, and the generated voltage on the AC side is Superimposed on the input voltage from the AC power supply. Then, only in the short-circuit phase range centered on the zero-cross phase of the phase of the input voltage from the AC power supply, the short-circuit switch is turned on to bypass the smoothing capacitor. (For example, refer to Patent Document 1).

JP 2009-95160 A (paragraphs 0032 to 0039 and FIGS. 10 to 12)

  In such a power converter, since the input current is controlled so that the input power factor is approximately 1 even while the shorting switch is turned on, the output voltage from the inverter circuit is opposed to the input voltage from the AC power supply. Thus, the operation of charging the DC voltage source of the inverter circuit is performed. Then, while the shorting switch is turned off, control is performed so that the output voltage of the inverter circuit is superimposed on the input voltage, thereby discharging the DC voltage source of the inverter circuit and charging the smoothing capacitor.

  However, when the AC power supply is disconnected during such a control operation and the input terminal of the power converter is opened, a voltage between the input terminals is output by the output of the inverter circuit. In particular, when a signal synchronized with the input voltage of the AC power supply is calculated inside the control circuit, current control is performed according to the synchronization signal and a short-circuit phase range is defined, control is performed with the synchronized frequency and phase even after the input terminal is opened. In order to continue, an AC voltage is generated between the input terminals by the output of the inverter circuit.

  In this way, since the voltage is output to the input terminal side despite the circuit configuration that performs power conversion in the power running direction, a person can move between the input terminals before the operation of the power conversion device is stopped after being opened. There is a risk of electric shock if touched. Accordingly, it is necessary to take measures such as detecting the opening of the input terminal and quickly stopping the operation. However, since the voltage generated at the input terminal is alternating current, there is a problem in that the presence or absence of the power source cannot be detected.

The present invention has been made to solve the above problems, and when the power supply is disconnected and the input terminal is opened, voltage is applied between the input terminals by the output of the inverter circuit. Even if it was made, it aims at providing the power converter device which detected that an input terminal was an open state.

In the power conversion device according to the present invention, one or more AC terminals of a single-phase inverter including a first input terminal and a second input terminal connected to a power source, a plurality of semiconductor switch elements and a DC voltage source are connected in series. An inverter circuit that connects the AC side in series to the first input terminal and superimposes the sum of the outputs of each single-phase inverter on the output of the power supply, and one or more switches connected between the DC buses One AC terminal is connected to the AC output line in the latter stage of the inverter circuit, the other AC terminal is connected to the second input terminal, and the AC terminals are connected so that they can be short-circuited by a switch. The converter circuit that outputs DC power to the DC bus, the smoothing capacitor that is connected between the DC buses and smoothes the output of the converter circuit, and the AC capacitor terminals are short-circuited to bypass the smoothing capacitor. Controls the short-circuit period for, and a control circuit for controlling the inverter circuit using the voltage or current command, if the power supply is disconnected, the inverter circuit between the first input terminal and a second input terminal A power conversion device in which an AC voltage is generated by an output , wherein the control circuit is connected to a power source based on a predetermined determination element generated in an inverter circuit, a converter circuit, or the like between the first input terminal and the second input terminal. Is provided with a power-off detection means for detecting that is disconnected.

  According to the present invention, since it is possible to detect that the power source has been disconnected, it is possible to take measures such as promptly stopping the operation. As a result, it is possible to prevent accidents such as an electric shock due to a voltage generated between terminals such as a plug connecting the power conversion device to the power source, and an electric shock in the security and maintenance of the power system.

It is a block diagram of the power converter device by Embodiment 1 of this invention. It is a current pathway diagram explaining operation | movement of the power converter device by Embodiment 1 of this invention. It is a 1st electric current route figure explaining operation | movement of the power converter device by Embodiment 1 of this invention. It is a 2nd electric current route figure explaining operation | movement of the power converter device by Embodiment 1 of this invention. It is a 3rd electric current route figure explaining operation | movement of the power converter device by Embodiment 1 of this invention. It is a figure which shows the waveform of each part explaining the operation | movement at the time of pressure | voltage rise of the power converter device by Embodiment 1 of this invention, and DC voltage source charging / discharging of an inverter circuit. It is a figure which shows the waveform of each part explaining the operation | movement at the time of pressure | voltage fall of the power converter device by Embodiment 1 of this invention, and DC voltage source charging / discharging of an inverter circuit. It is a control block diagram which shows the inverter circuit control of the power converter device by Embodiment 1 of this invention. It is a control block diagram which shows converter circuit control of the power converter device by Embodiment 1 of this invention. It is a figure explaining the waveform of each part at the time of the input terminal open | release of the power converter device by Embodiment 1 of this invention. It is a figure explaining the waveform of each part at the time of the input terminal open | release of the power converter device by Embodiment 1 of this invention. It is a current pathway diagram explaining the operation | movement at the time of the input terminal open | release of the power converter device by Embodiment 1 of this invention. It is a figure which shows the flowchart explaining the power-off detection means of the power converter device by Embodiment 1 of this invention. It is a figure which shows the flowchart explaining the power-off detection means of the power converter device by Embodiment 3 of this invention. It is a figure explaining the waveform of each part at the time of the input terminal open | release of the power converter device by Embodiment 3 of this invention, and the time of a power-off detection.

Embodiment 1 FIG.
Hereinafter, the power converter in Embodiment 1 of this invention is demonstrated based on figures. 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, the power conversion device includes a main circuit and a control circuit 10 for converting the AC power of the AC power source 1 into DC power and outputting it.

The main circuit includes an input filter circuit 4, a reactor 2 as a current limiting circuit, an inverter circuit 100, a converter circuit 300, and a smoothing capacitor 3. The AC power source 1 is connected between the first input terminal t1 and the second input terminal t2 of the power converter, and the first input terminal t1 is connected to the reactor 2 via the input filter circuit 4, and is connected to the subsequent stage. The AC side of the inverter circuit 100 configured with a single-phase inverter is connected in series.
In the converter circuit 300, one AC terminal is connected to the AC output line at the rear stage of the inverter circuit 100, and the other AC terminal is connected to the second input terminal t 2 via the input filter circuit 4. DC power is output to the smoothing capacitor 3 connected between the buses 3a and 3b.

  Here, the input filter circuit 4 is assumed to be a filter in which a capacitor is inserted between input terminals in order to remove normal mode noise. However, it may be a filter circuit having other elements and configurations such as a common mode choke coil and a surge absorber.

  The single-phase inverter in the inverter circuit 100 includes semiconductor switch elements 101a to 104a such as a plurality of MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) each including a diode 101b to 104b between a source and a drain, and a DC capacitor. This is an inverter having a full bridge configuration constituted by the DC voltage source 105.

The converter circuit 300 includes semiconductor switch elements 302a and 304a connected between the DC buses 3a and 3b. In this case, the semiconductor switch elements 302a and 304a such as MOSFETs incorporating the diodes 302b and 304b and the diodes 301 and 303 are included. Are connected in series between the DC buses 3a and 3b.
A connection point between the anode of the diode 301 of the converter circuit 300 and the drain of the semiconductor switch element 302a is connected to the AC output line at the subsequent stage of the inverter circuit 100. A connection point between the anode of the diode 303 and the drain of the semiconductor switch element 304a is connected to the second input terminal t2 through the input filter circuit 4.

  The semiconductor switch elements 101a to 104a, 302a, and 304a may be IGBTs (Insulated Gate Bipolar Transistors) in which diodes are connected in antiparallel in addition to MOSFETs. The reactor 2 may be connected in series between the inverter circuit 100 and the converter circuit 300, or between the converter circuit 300 and the second input terminal t2. Further, mechanical switches may be used instead of the semiconductor switch elements 302a and 304a of the converter circuit 300.

The control circuit 10 includes a voltage Vsub of the DC voltage source 105 of the inverter circuit 100, a voltage Vdc of the smoothing capacitor 3, an input voltage Vin applied between the input terminals t1 and t2 of the power converter, and an input current flowing to the input terminal. Based on Iin, the gate signal 11 to each of the semiconductor switch elements 101a to 104a, 302a, 304a in the inverter circuit 100 and the converter circuit 300 so that the voltage Vdc of the smoothing capacitor 3 becomes a constant target voltage Vdc *, 12 is generated to control the output of the inverter circuit 100 and the converter circuit 300.

The smoothing capacitor 3 is connected to a load (not shown). In normal times, the voltage Vdc is lower than the target voltage Vdc *, and the control circuit 10 converts the AC power from the AC power source 1 and supplies the DC power to the smoothing capacitor 3. The inverter circuit 100 and the converter circuit 300 are output controlled so as to be supplied.
In addition, the control circuit 10 includes power-off detection means 1000 that detects that the connection between the AC power source 1 and the input terminals t1 and t2 is disconnected based on a predetermined determination element described later.

  The operation of the power conversion device configured as described above will be described with reference to FIGS. 2 to 5 show current path diagrams in the power conversion operation. FIG. 6 is a diagram showing the waveforms of the respective parts and the charging / discharging of the DC voltage source 105 of the inverter circuit 100 for explaining the operation at the time of boosting of the power converter. FIG. 7 is a diagram showing the waveforms of the respective parts and the charging / discharging of the DC voltage source 105 of the inverter circuit 100 for explaining the operation at the time of step-down of the power converter.

The case where the voltage Vdc of the output stage smoothing capacitor 3 is higher than the peak voltage Vp of the input voltage Vin from the AC power supply 1 is referred to as boosting, and the voltage Vdc of the output stage smoothing capacitor 3 is input from the AC power supply 1. The case where the voltage Vin is lower than the peak voltage Vp is called step-down.
6 and 7 show a state where the voltage Vdc of the smoothing capacitor 3 is controlled to a constant target voltage Vdc *. The voltage Vin from the AC power supply 1 has a waveform as shown in FIGS. The inverter circuit 100 controls and outputs the current Iin by PWM control so that the 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 that is the output of the AC power supply 1. .

First, the case where the voltage phase of the AC power supply 1 is θ and the voltage Vin is positive polarity 0 ≦ θ <π will be described.
In the inverter circuit 100, when the semiconductor switch elements 101a and 104a are on and the semiconductor switch elements 102a and 103a are off, a current flows so as to charge the DC voltage source 105, and the semiconductor switch elements 102a and 103a are on. When 101a and 104a are off, a current flows so as to discharge the DC voltage source 105.

  Further, when the semiconductor switch elements 101a and 103a are on, the semiconductor switch elements 102a and 104a are off, and when the semiconductor switch elements 102a and 104a are on and the semiconductor switch elements 101a and 103a are off, the DC voltage source 105 is passed through. Current flows. The control circuit 10 controls the semiconductor switch elements 101a to 104a with such a combination of four types of control, and performs the PWM operation of the inverter circuit 100 to charge / discharge the DC voltage source 105 to perform current control.

  As shown in FIG. 2, the current from the AC power source 1 is limited by the reactor 2 and input to the inverter circuit 100, and the output passes through the diode 301 in the converter circuit 300 to charge the smoothing capacitor 3 and the diode 304b. Then, the AC power source 1 is returned. At this time, the control circuit 10 performs current control by discharging or charging / discharging the DC voltage source 105 by causing the inverter circuit 100 to perform PWM operation by a combination of the above four types of control.

In FIG. 6, with the zero cross phase of the input voltage Vin from the AC power supply 1 as the center, ± θ
_In the phase range of ₁ (hereinafter referred to as the short circuit period T), as shown in FIG. 3, the control circuit 10 bypasses the smoothing capacitor 3 by turning on the semiconductor switch element 302a serving as a short circuit switch in the control of the converter circuit 300. Let The current from the AC power source 1 is limited in the reactor 2 and is input to the inverter circuit 100 to charge the DC voltage source 105, and returns to the AC power source 1 through the semiconductor switch element 302 a and the diode 304 b in the converter circuit 300. At this time, the control circuit 10 performs the current control by charging the DC voltage source 105 by performing the PWM operation of the inverter circuit 100 by a combination of the above four types of control.

Next, the case where π ≦ θ <2π where the voltage Vin is negative will be described.
In the inverter circuit 100, when the semiconductor switch elements 102a and 103a are on and the semiconductor switch elements 101a and 104a are off, a current flows so as to charge the DC voltage source 105, and the semiconductor switch elements 101a and 104a are on. When 102a and 103a are off, a current flows so as to discharge the DC voltage source 105.
Further, when the semiconductor switch elements 101a and 103a are on, the semiconductor switch elements 102a and 104a are off, and when the semiconductor switch elements 102a and 104a are on and the semiconductor switch elements 101a and 103a are off, the DC voltage source 105 is passed through. Current flows. The control circuit 10 performs the current control by charging and discharging the DC voltage source 105 by controlling the semiconductor switch elements 101a to 104a and performing the PWM operation of the inverter circuit 100 by the combination of the four types of controls.

  As shown in FIG. 4, the current from the AC power supply 1 passes through the diode 303 in the converter circuit 300, charges the smoothing capacitor 3, and is input to the inverter circuit 100 through the diode 302b. The output of the inverter circuit 100 is the reactor. 2 to return to the AC power source 1. At this time, the control circuit 10 performs current control by discharging or charging / discharging the DC voltage source 105 by causing the inverter circuit 100 to perform PWM operation by a combination of the above four types of control.

  In the short circuit period T, as shown in FIG. 5, the control circuit 10 bypasses the smoothing capacitor 3 by turning on the semiconductor switch element 304 a that is a short circuit switch in the control of the converter circuit 300. The current from the AC power source 1 is input to the inverter circuit 100 through the semiconductor switch element 304a and the diode 302b of the converter circuit 300, charges the DC voltage source 105, and returns to the AC power source 1 through the reactor 2. At this time, the control circuit 10 performs the current control by charging the DC voltage source 105 by performing the PWM operation of the inverter circuit 100 by a combination of the above four types of control.

  In the control of the converter circuit 300, the control circuit 10 is turned on only when the semiconductor switch elements 302a and 304a are operated as short-circuit switches. However, when current is passed through the diodes 302b and 304b, the diodes are reversed. The semiconductor switch elements 302a and 304a connected in parallel may be turned on so that a current flows through the semiconductor switch elements 302a and 304a. That is, the two semiconductor switch elements 302a and 304a may be turned on as a short circuit switch in the short circuit period T regardless of whether the voltage Vin is positive or negative.

As shown in FIG. 6, the inverter circuit 100 outputs a voltage (−Vin) in the short-circuit period T to charge the DC voltage source 105 with the AC power source 1 and then charge the DC voltage source 105 during the voltage step-up of the power conversion device. , Θ ₁ ≦ θ <π−θ _1, when the DC voltage source 105 is discharged, the output voltage of the inverter circuit 100 (Vdc * −Vin) is added to the input voltage Vin from the AC power supply 1. The voltage Vdc of the smoothing capacitor 3 is controlled to a target voltage Vdc * higher than the peak voltage of the AC power supply 1.

Further, at the time of step-down of the power conversion device, as shown in FIG. 7, the inverter circuit 100 outputs a voltage (−Vin) in the short-circuit period T and charges the DC voltage source 105 with the AC power source 1, and then the AC power source. By adding the output voltage of the inverter circuit 100 to the input voltage Vin from 1, the voltage Vdc of the smoothing capacitor 3 is controlled to the target voltage Vdc * lower than the peak voltage of the AC power supply 1.
Assuming that the phase θ = θ ₂ (0 <θ ₂ <π / 2) when the input voltage Vin from the AC power source 1 becomes equal to the target voltage Vdc * of the smoothing capacitor 3, θ ₁ ≦ θ <θ ₂ , π− When θ ₂ ≦ θ <π−θ ₁ , the inverter circuit 100 outputs a voltage (Vdc * −Vin) to discharge the DC voltage source 105, and when θ ₂ ≦ θ <π−θ ₂ , The circuit 100 outputs a voltage (Vin−Vdc *) to charge the DC voltage source 105.

As described above, the control circuit 10 switches the control of the converter circuit 300 at the zero cross phase (θ = 0, π) ± θ ₁ of the voltage phase θ of the AC power supply 1, and ± θ ₁ with the zero cross phase as the center. Only in the short-circuit period T, which is the phase range of, the smoothing capacitor 3 is bypassed by turning on the semiconductor switch elements 302a and 304a serving as short-circuit switches. At this time, the control circuit 10 controls the output of the inverter circuit 100 by controlling the current Iin so that the input power factor is approximately 1, while generating a voltage substantially equal to the reverse polarity of the voltage Vin from the inverter circuit 100. The DC voltage source 105 is charged.

  In the phase other than the short-circuit period T, the control circuit 10 maintains the DC voltage Vdc of the smoothing capacitor 3 at the target voltage Vdc *, and controls the current Iin so that the input power factor is approximately 1, thereby controlling the inverter circuit. 100 is output-controlled. 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 3, the DC voltage source 105 is discharged. When the absolute value of the voltage Vin is equal to or higher than the target voltage Vdc *, the DC voltage source 105 is charged. Is done.

In the short-circuit period T, the zero-cross phase (θ = 0, π) is the center of the short-circuit period T. However, the short-circuit period T may be deviated to any one of the phase ranges including the zero-cross phase.
Further, the phase range of the short-circuit period T can be determined so that the charging and discharging energies of the DC voltage source 105 of the inverter circuit 100 are equal. Assuming that the charging / discharging energy of the DC voltage source 105 of the inverter circuit 100 is equal, the following formula is established when Vdc * <Vp. However, Vp is the peak voltage of the voltage Vin, and Ip is the peak current of the current Iin.

Here, when Vin = Vp · sin θ and Iin = Ip · sin θ,
Vdc * = Vp · π / (4 cos θ ₁ )
Thus, the lower limit value of Vdc * is when θ ₁ is 0, and the value is (π / 4) Vp.
As described above, the target voltage Vdc * of the smoothing capacitor 3 is determined by θ ₁ that determines the phase range of the short circuit period T, that is, can be controlled by changing θ ₁ . The DC voltage Vdc of the smoothing capacitor 3 is controlled so as to follow the target voltage Vdc *.

Next, voltage conditions of the DC voltage source 105 of the inverter circuit 100 will be described.
The voltage Vsub of the DC voltage source 105 is 0 ≦ θ <θ ₁ and θ ₁ ≦ θ <π / 2 at the time of boosting, and 0 ≦ θ <θ ₁ , θ ₁ ≦ θ <θ ₂ , θ at the time of stepping down. The inverter circuit 100 can perform the above-described desired control with high reliability by setting it to be equal to or greater than the desired generated voltage of the inverter circuit 100 in each phase range of ₂ ≦ θ <π / 2. That is, the voltage V of the DC voltage source 105
The sub needs to satisfy the following expressions (2), (3), and (4).
Vsub ≧ Vp · sin θ ₁ (2)
Vsub ≧ (Vdc * −Vp · sin θ ₁ ) (3)
Vsub ≧ (Vp−Vdc *) (4)

The voltage Vsub of the DC voltage source 105 is set to be equal to or lower than the peak voltage Vp of the input voltage Vin from the AC power supply 1. In the inverter circuit 100 that performs PWM control, the loss increases as the voltage Vsub of the DC voltage source 105 increases. Therefore, it is desirable to set the voltage Vsub to a small value under the conditions satisfying the above three expressions (2), (3), and (4). .
Then, by the zero cross phase and short circuit period T to bypass only the smoothing capacitor 3 phase range of ± theta ₁ as a central, inverter circuit 100, even the short circuit period T, the input power factor is approximate in other periods of 1 Thus, the current Iin can be controlled so that the DC power of a desired voltage can be output to the smoothing capacitor 3.

Next, details of the control of the inverter circuit 100 will be described with reference to FIG. FIG. 8 is a control block diagram in the output control of the inverter circuit 100 by the control circuit 10.
By controlling the output of the inverter circuit 100, the DC voltage Vdc of the smoothing capacitor 3 is maintained at the target voltage Vdc *, and the current Iin is controlled so that the power factor of the AC power supply 1 is approximately 1. First, the difference 21 between the DC voltage Vdc and the target voltage Vdc * of the smoothing capacitor 3 is used as a feedback amount, the PI-controlled output is set as the amplitude target value 22, and the voltage from the AC power supply synchronization frequency is determined based on the amplitude target value 22. A sine wave current command Iin * synchronized with Vin is generated. Next, using the difference 24 between the current command Iin * and the detected current Iin as a feedback amount, the PI-controlled output is set as a voltage command 25 that becomes a target value of the voltage generated by the inverter circuit 100.

At this time, at the time of switching between the control of the short-circuit period T that short-circuits the AC terminals of the converter circuit 300 and the control that conducts between each AC terminal of the converter circuit 300 and the smoothing capacitor 3, that is, control other than the short-circuit period T. The voltage feed 25 is corrected by adding the synchronized feedforward correction voltage ΔV. As a result, it is possible to reliably prevent the delay of the control by the response time of the feedback control, and it is possible to control the current Iin so that the input power factor becomes approximately 1 even when switching to other than the short-circuit period. Current fluctuation can be suppressed with high reliability, and generation of harmonic current can be suppressed.
Then, using the corrected voltage command 26, the PWM control unit 27 generates the gate signal 11 to each of the semiconductor switch elements 101a to 104a of the inverter circuit 100, and operates the inverter circuit 100.

Next, output control of the converter circuit 300 and control for causing the voltage Vsub of the DC voltage source 105 of the inverter circuit 100 to follow the command value Vsub * will be described below with reference to FIG. FIG. 9 is a control block diagram in the output control of the converter circuit 300 by the control circuit 10.
First, the PWM control unit 34 uses the difference 32 between the set command value Vsub * and the detected voltage Vsub as a feedback amount and the PI-controlled output 33 as a voltage command to each of the semiconductor switch elements 302a and 304a of the converter circuit 300. The gate signal 12 is generated. The PWM control unit 34 performs a comparison operation using a triangular wave (AC power supply synchronization triangular wave) 35 synchronized with a cycle twice the frequency of the AC power supply 1 as a carrier wave, and compares the calculated signal with the polarity of the AC power supply 1. A gate signal 12 is generated that operates in the middle of the phase where the input voltage Vin from the AC power supply 1 zero-crosses. That is, the short-circuit period T in which the AC signals of the converter circuit 300 are short-circuited by the gate signal 12 is also controlled, and the short-circuit period T is long when the voltage Vsub is lowered, and the short-circuit period T is short when the voltage Vsub is increased. Is done.

In order to control the current when the control circuit 10 turns on the short-circuit switch of the converter circuit 300 from the OFF state by the gate signal 12 at the zero cross phase −θ ₁ of the input voltage Vin from the AC power supply 1, Vp · | sin θ ₁ It is necessary to satisfy the voltage condition of | <Vsub. From the viewpoint of current control, the PWM control unit 34 restricts the short-circuit switch from being turned on when the voltage Vsub of the DC voltage source 105 of the inverter circuit 100 drops and the voltage condition is not satisfied. Then, after the phase of the voltage Vin approaches the zero cross phase and becomes | Vin | <Vsub, the short circuit switch is turned on.

In such a power conversion device that operates under the control of the control circuit 10, when the AC power source 1 is disconnected during operation and the input terminals t 1 and t 2 are opened, the power-off detection means 1000 of the control circuit 10. Thus, the opening of the input terminals t1 and t2 is detected.
First, the operation when the input terminals t1 and t2 are opened during the operation of the power converter will be described below with reference to FIGS. 10 and 11 show the waveforms of the input voltage Vin and the input current Iin when the input terminal is open, the on / off state of the short-circuit switch, and the AC synchronous sine wave. The AC synchronized sine wave shown here is a sine wave generated based on the AC power supply synchronization frequency, and the short-circuit switch is turned on by the above-described control before and after the zero cross of the AC synchronized sine wave.

10 and 11 both show examples of waveforms when the input terminal is opened. However, in FIG. 11, the voltage condition deviates from the condition of | Vin | <Vsub, and the short-circuit switch is forced. Operation when turning off automatically.
FIG. 12 shows a current path when the short-circuit switch is turned on and the current command Iin * is positive when the input terminal is opened.

  In FIG. 10, since the AC power supply 1 is disconnected when the input terminal is opened, the input current Iin cannot be controlled immediately after being opened, and becomes 0A. However, the control to follow the current command Iin * is continued, and an AC voltage different from the AC power supply 1 appears in the input voltage Vin by switching the inverter circuit 100. The voltage value generated in the input voltage Vin at this time will be described by being divided into periods indicated by T1 to T4.

  T1 is a period during which the AC synchronous sine wave is positive and the short-circuit switch is on. In this period T1, since the current command Iin * is positive, the input current Iin is controlled in the positive direction. At this time, since the output of the inverter circuit 100 is controlled so that current flows through the path shown in FIG. 12, the input voltage Vin increases in the negative direction, and the input voltage Vin is a voltage (−Vsub) which is the maximum output voltage of the inverter circuit 100. ).

  T2 is a period in which the AC synchronous sine wave is positive and the short-circuit switch is off. In this period T2, the smoothing capacitor 3 is charged by adding the output of the inverter circuit 100 to the input voltage Vin in accordance with the positive current command Iin *. The input voltage Vin at this time is the voltage (−Vsub). Therefore, even if the voltage (Vsub) is output from the inverter circuit 100, no current flows through the circuit, and the input voltage Vin does not change.

T3 is a period in which the AC synchronous sine wave is negative and the short-circuit switch is on. In this period T3, an operation in which the polarity is inverted with respect to the period T1 is performed. That is, the input voltage Vin increases in the positive direction, and the input voltage Vin becomes equal to the voltage (Vsub) that is the maximum output voltage of the inverter circuit 100.
T4 is a period in which the AC synchronous sine wave is negative and the short-circuit switch is off. In this period T4, an operation in which the polarity is inverted with respect to the period T2 is performed. That is, since the input voltage Vin is the voltage (Vsub), even when the voltage (−Vsub) is output from the inverter circuit 100, no current flows through the circuit, and the input voltage Vin does not change.

FIG. 11 shows an operation in which an AC voltage is generated in the input voltage Vin when the input terminal is opened as in FIG. 10, but the above condition of voltage | Vin | <Vsub is not satisfied, and the short-circuit switch is forcibly turned off. The case of performing will be described separately for the periods indicated by T5 to T8.
T5 is a period in which the AC synchronous sine wave is positive and the short-circuit switch is off. In this period T5, the smoothing capacitor 3 is charged by adding the output of the inverter circuit 100 to the input voltage Vin in accordance with the positive current command Iin *.
Since the input voltage Vin at this time is a voltage (Vsub), when the voltage (Vsub) is superimposed from the inverter circuit 100 and becomes equal to or higher than the DC voltage Vdc of the smoothing capacitor 3, electric power is output. However, since there is only the charge of the filter capacitor of the input filter circuit 4 between the input terminals, the input voltage Vin instantaneously drops to the voltage (Vdc−Vsub).

T6 is a period during which the AC synchronous sine wave is positive and the short-circuit switch is turned off. In this period T6, since the current command Iin * is positive, the operation of controlling the input current Iin in the positive direction is performed. At this time, since the output of the inverter circuit 100 is controlled so that current flows through the path shown in FIG. 12, the input voltage Vin increases in the negative direction.
Then, the voltage of the input voltage Vin is increased by the operation of discharging the charge of the DC voltage source 105 of the inverter circuit 100, and the discharge operation is instantaneously maintained by the reactor 2, so that the condition | Vin | <Vsub is satisfied. The short circuit switch is turned off. Since the input voltage Vin is approximately the voltage (−Vsub) until the current command Iin * becomes negative after the short-circuit switch is turned off, that is, until the zero cross of the AC synchronous sine wave, the voltage (Vsub) is supplied from the inverter circuit 100. Even if output, no current flows through the circuit, and the input voltage Vin does not change.

T7 is a period in which the AC synchronous sine wave is negative and the short-circuit switch is off. In this period T7, an operation in which the polarity is inverted with respect to the period T5 is performed. That is, the input voltage Vin instantaneously decreases to the voltage (−Vdc + Vsub).
T8 is a period during which the AC synchronous sine wave is negative and the short-circuit switch is turned off. In this period T8, an operation in which the polarity is inverted with respect to the period T6 is performed. That is, the input voltage Vin increases in the positive direction, deviating from the condition of | Vin | <Vsub, and the short-circuit switch is turned off. The input voltage Vin does not change from the voltage (Vsub) until the zero cross of the AC synchronous sine wave.

Next, as shown in FIGS. 10 and 11, when the AC voltage is generated in the input voltage Vin when the input terminal is open, the power-off detection unit 1000 that detects that the input terminal is open is shown in the flowchart of FIG. Will be described. The process shown in the flowchart of FIG. 13 is applied during the operation of the control.
First, in step S50, it is determined whether the period variation between zero crosses of the input voltage Vin is equal to or greater than the period variation threshold T _TH . Since the zero-cross timing of the input voltage Vin changes when the input terminal is open, the period change amount is included as a determination condition for detecting power-off. The period change amount is calculated from the difference between the period at a certain point in time and the period detected one time before.

If no change has occurred in the zero crossing of the input voltage Vin in step S50 (NO), the process ends.
Further, if the condition is met in step S50 (YES), the process proceeds to step S51, determines whether input current Iin is lower than the current threshold _{I TH,} and to the duration t _OPEN or more. Since the current detected as the input current Iin when the input terminal is opened is a slight current value generated by the charge transfer of the capacitor constituting the input filter circuit 4, the continuation of the decrease in the input current Iin is included as a judgment condition for detecting power-off. .

In step S51, the input current Iin is equal to or greater than the current threshold _{I TH} (NO), the process ends.
If the condition in step S51 is matched (YES), the process proceeds to step S52, and it is determined whether the effective value of the current command Iin * is equal to or greater than the current effective value threshold Irms _TH . Although the input current Iin is decreased when the input terminal opened, when the current command Iin * is set to less than the current threshold I _TH of step S51 is always matches the condition of step S51.

Therefore, if power-off is detected according to the conditions up to step S51, there is a possibility that power-off is erroneously detected due to an erroneous determination of the period change in step S50. Therefore, it is determined that the input current Iin is decreasing although the current command Iin * is set to a sufficiently high value according to the condition of step S52. The current effective value threshold Irms _TH is considering the control error is set to a value higher than the current threshold I _TH in Step S51, to be able to determine the input current Iin decreases at the input terminal opened.

If the condition in step S52 is met (YES), the process proceeds to step S53, the power-off is detected, and the process ends.
If the condition in step S52 is not met (NO), the process proceeds to step S54, and it is determined whether the effective value change amount of the input voltage Vin is equal to or greater than the voltage effective value threshold value Vrms _TH . When the input terminal is open, the maximum value of the voltage generated in the input voltage Vin depends on the voltage of the DC voltage source 105 of the inverter circuit 100, and thus has a voltage effective value different from the AC voltage of the AC power supply 1. As a result, when the current command Iin * is set low and power-off cannot be detected under the condition of step S52, the power-off is determined based on the effective value change amount of the input voltage Vin.

Note that the effective value change amount of the input voltage Vin can be obtained by subtracting the Vin effective value after the change from the Vin effective value before the change, but depending on the timing of the Vin effective value calculation, it includes before and after the input terminal is opened. The effective value change amount can be obtained accurately by ignoring the effective value calculated in the period when the input terminal is opened.
If the condition in step S54 is met (YES), the process proceeds to step S53, the power-off is detected, and the process is terminated.
Also must match the condition at step S54 (NO), the process proceeds to step S55, and determines whether the phase difference integrated value of the alternating current synchronous sinusoidal input voltage Vin is the phase difference accumulation threshold phi _TH or more.

In the process of step S54, even if the amount of change in the effective value of the input voltage Vin is less than the threshold value Vrms _TH , there is a possibility that the input voltage Vin when the input terminal is open matches the effective value of the AC voltage of the AC power source 1. Therefore, in step S55, a condition for detecting power-off from the AC waveform of the input voltage Vin is set.
The phase difference integrated value is a value obtained by integrating the phase difference between the AC voltage generated by the input voltage Vin and the AC synchronous sine wave for a predetermined period such as between zero crosses, and the degree to which the AC waveform of the input voltage Vin differs from the sine wave is simplified. Numerically.
If the condition in step S55 is met (YES), the process proceeds to step S53, the power-off is detected, and the process is terminated. If the condition in step S55 is not met (NO), it is determined that the power is not turned off, and the process ends.

  When the control circuit 10 detects that the AC power source 1 has been disconnected from the power converter by the power-off detection means 1000, the semiconductor switch elements 101a to 104a, 302a, 304a in the inverter circuit 100 and the converter circuit 300 are detected. Are turned off to stop the switching operation.

In this embodiment, the control circuit 10 uses the current command Iin * to generate an inverter circuit 10
By controlling 0, the voltage Vdc of the smoothing capacitor 3 is made to follow the target voltage Vdc *, and the power factor of the AC power source 1 is controlled to be improved.
Since the converter circuit 300 does not require high frequency switching, there is almost no switching loss. Further, the inverter circuit 100 that operates so as to control the power factor and control the DC voltage Vdc of the smoothing capacitor 3 can significantly reduce the voltage Vsub handled by switching from the peak voltage of the AC power supply 1. For this reason, switching loss and noise can be reduced without requiring a large reactor 2, and the reliability of the elements of the inverter circuit 100 is improved.

  Further, the control circuit 10 has a short circuit period T that bypasses the smoothing capacitor 3 to control the converter circuit 300, and the DC voltage source 105 is charged in the short circuit period T in the inverter circuit 100. Therefore, the inverter circuit 100 can control the current without generating a high voltage, and can use the energy charged in the DC voltage source 105 for discharging the smoothing capacitor 3. For this reason, in the inverter circuit 100, the voltage handled by switching can be further reduced, and higher efficiency and lower noise can be further promoted.

  In addition, when the AC power supply 1 is disconnected and the input terminals t1 and t2 are opened, an AC voltage is generated in the input voltage Vin by the output of the inverter circuit 100. Therefore, the control circuit 10 includes the power-off detection means 1000, and the input terminal It is possible to take measures such as detecting that the power converter is in an open state and quickly stopping the operation of the power converter upon receiving this power-off detection. As a result, it is possible to prevent accidents such as an electric shock due to a voltage generated between terminals such as a plug connecting the power conversion device to the power source, and an electric shock in the security and maintenance of the power system.

The power-off detection unit 1000 detects power-off based on a determination as to whether or not the period variation between zero crosses of the input voltage Vin is equal to or greater than the period variation threshold T _TH . As a result, a change in the input voltage Vin when the power is turned off can be detected immediately, and the power supply can be detected quickly.
Note that, as a determination element, instead of the periodical change amount between zero crosses of the input voltage Vin, the power-off may be detected when the change amount of the frequency of the input voltage Vin is equal to or higher than the frequency change threshold. That is, the change in the period is a change in the frequency, and the power-off can be detected in the same manner as the period change amount.

Further, the power-off detection unit 1000 detects a power-off based on the determination of whether the input current Iin is lower than the current threshold I _TH, and to the duration t _OPEN or more. As described above, by making a determination based on the input current Iin that changes characteristically when the power is turned off, it is possible to quickly detect the power-off.

Further, the power-off detection means 1000 detects power-off based on a determination as to whether the effective value change amount of the input voltage Vin is equal to or greater than the voltage effective value threshold value Vrms _TH . As a result, a change in the input voltage Vin when the power is turned off can be detected immediately, and the power supply can be detected quickly.
The power-off detection means 1000 detects power-off based on the determination whether the phase difference integrated value between the input voltage Vin and the AC synchronous sine wave is equal to or greater than the phase difference integration threshold φ _TH . As a result, a change in the input voltage Vin when the power is turned off can be detected immediately, and the power supply can be detected quickly.

  Further, the power-off detection means 1000 combines a plurality of determination elements such as the voltage value, period, frequency, phase, and input current Iin of the input voltage Vin as shown in the flowchart of FIG. The power-off is determined based on the above. Thereby, power-off can be detected with high accuracy.

Embodiment 2. FIG.
Next, a power converter according to Embodiment 2 of the present invention will be described. The schematic configuration diagram of the power conversion device according to the second embodiment is the same as FIG. 1 shown in the first embodiment, and the control circuit 1
The only difference is the determination element that is input to the zero power-off detection means 1000. Therefore, the description of the configuration is omitted.

In the first embodiment, the power-off detection unit 1000 determines the power-off based on the determination factors such as the voltage value, period, frequency, phase, and input current Iin of the input voltage Vin. The determination method is not limited to the method, and any determination method that can capture a characteristic change when the power is turned off may be used.
That is, the power-off detection unit 1000 according to the second embodiment may detect the disconnection of the input power based on the input power. For example, by detecting power-off based on the determination that the amount of decrease in input power within a predetermined period is greater than or equal to a predetermined threshold, it is possible to quickly detect power-off based on a characteristic change in input power at the time of power-off. Can do.

Further, the power cut-off detection means 1000 may be one that detects the cut-off of the input power based on the voltage Vdc of the smoothing capacitor 3. For example, during the output of DC power to the load, the voltage of the smoothing capacitor 3 at the time of power-off is detected by detecting power-off based on the determination that the amount of decrease in the voltage Vdc of the smoothing capacitor 3 within a predetermined period is greater than or equal to a predetermined threshold. Based on the characteristic change of Vdc, it is possible to quickly detect power-off.

  Further, the power cut-off detection means 1000 may detect the cut-off of the input power based on the current Icon outputted from the converter 300. For example, based on a characteristic change in the current Icon output from the converter 300 when the power is turned off by detecting power off based on the determination that the amount of decrease in the current Icon output from the converter 300 is greater than or equal to a predetermined threshold. A power-off can be detected promptly.

  Further, the power-off detection means 1000 may detect the disconnection of the input power based on the voltage Vsub of the DC voltage source 105 of the inverter circuit 100. For example, a characteristic change in the voltage Vsub of the DC voltage source 105 at the time of power-off is detected by detecting power-off based on the determination that the amount of decrease in the voltage Vsub of the DC voltage source 105 within a predetermined period is greater than or equal to a predetermined threshold. Based on this, it is possible to quickly detect power-off.

  Further, the power-off detection means 1000 may detect the disconnection of the input power based on the current flowing through the DC voltage source 105 of the inverter circuit 100. For example, by detecting power-off based on the determination that the current flowing through the DC voltage source 105 is less than a predetermined threshold regardless of whether the short-circuit switch is on or off, the DC voltage source 105 at the time of power-off is detected. Based on the characteristic change of the current, it is possible to quickly detect the power-off.

In addition to using the above-described determination factors such as the input power, the voltage Vdc of the smoothing capacitor 3, the current Icon that is output from the converter 300, the voltage Vsub of the DC voltage source 105, and the current flowing through the DC voltage source 105, A plurality of determination elements may be combined, and the power-off may be determined based on the plurality of determination elements. Further, the power-off may be determined by combining the determination element described in the first embodiment and the determination element described in the second embodiment. Thereby, power-off can be detected with high accuracy.

Further, when the control circuit 10 detects the power-off by the power-off detection means 1000, the control circuit 10 immediately stops the control by turning off each of the semiconductor switch elements, but after the control is continued for a while so that the input voltage Vin decreases. You may stop. For example, when the switching control is continued even after the power-off detection means 1000 detects the power-off, and the voltage value generated between the first input terminal t1 and the second input terminal t2 becomes a predetermined threshold value or less, All semiconductor switch elements and switches are turned off to stop the control.
Thus, by stopping the control when the input voltage Vin decreases to a predetermined threshold value or less, the risk of electric shock when contacting between the input terminals can be reduced.

Embodiment 3 FIG.
Next, a power conversion device according to Embodiment 3 of the present invention will be described with reference to FIGS.
The schematic configuration diagram of the power conversion device according to the third embodiment is the same as FIG. 1 shown in the first embodiment. Further, the control of inverter circuit 100 and the control of converter circuit 300 of the power conversion device according to the third embodiment are the same as those in FIGS. 8 and 9 described in the first embodiment, and the description thereof is omitted.

The power-off detection means 1000 in this Embodiment 3 is demonstrated using the flowchart of FIG.
First, in step S60, it is determined whether or not the period variation amount between zero crosses of the input voltage Vin is equal to or greater than the period variation threshold T _TH . Since the zero-cross timing of the input voltage Vin changes when the input terminal is open, the period change amount is included as a determination condition for detecting power-off. The period change amount is calculated from the difference between the period at a certain point in time and the period detected one time before.

In step S60, if there is no change in the zero cross of the input voltage Vin (NO), the process ends.
If the condition in step S60 is met (YES), the process proceeds to step S61, the power-off is detected, and the process ends.
When the control circuit 10 detects that the AC power source 1 has been disconnected from the power converter by the power-off detection means 1000, a switching method in the case where the inverter circuit 100 outputs a voltage so as to face the input voltage Vin. Is changed so that all the semiconductor switch elements 101a to 104a of the inverter circuit 100 are turned off.

Specifically, when the input voltage Vin is positive, when the semiconductor switch elements 101a and 104a are turned on and the semiconductor switch elements 102a and 103a are turned off, the output of the inverter circuit 100 faces the input voltage Vin. When the input voltage Vin is negative, when the semiconductor switch elements 102a and 103a are turned on and the semiconductor switch elements 101a and 104a are turned off, the output of the inverter circuit 100 faces the input voltage Vin.
Thus, when the output control is performed so that the inverter circuit 100 is opposed to the input voltage Vin, all the semiconductor switch elements 101a to 104a of the inverter circuit 100 are turned off. That is, the inverter circuit 100 is subjected to PWM control by adding a combination of turning off all the semiconductor switch elements 101a to 104a to the above four types of control combinations.

If the input current Iin is controlled so that the input power factor is approximately 1, when all the semiconductor switch elements 101a to 104a of the inverter circuit 100 are turned off, the output of the inverter circuit 100 is the input voltage Vin. It becomes the voltage opposite to.
The operation when the input terminal is opened by such control will be described below with reference to FIG. FIG. 15 shows the waveforms of the input voltage Vin and the input current Iin, the ON / OFF state of the short-circuit switch, and the AC synchronous sine wave. The voltage value generated in the input voltage Vin immediately after the AC power source 1 is disconnected by opening the input terminal and the power source disconnection detecting means 1000 detects the power source disconnection will be described by dividing it into periods T9 to T12.

T9 is a period in which the AC synchronous sine wave is negative and the short-circuit switch is off. In this period T9, the inverter circuit 100 is supplied to the input voltage Vin according to the negative current command Iin *.
The smoothing capacitor 3 is charged by superimposing the output.
Here, since the input voltage Vin is a voltage (Vsub), the inverter circuit 100 outputs a voltage (−Vsub) or more opposite to the input voltage Vin, that is, all the semiconductor switch elements 101a to 104a of the inverter circuit 100 are controlled. PWM control is performed with the off state as 100%. At this time, the input current Iin cannot be controlled in the negative direction, and the input voltage Vin does not change.

  T10 is a period in which the AC synchronous sine wave is negative and the short-circuit switch is on. In this period T10, since the current command Iin * has a negative polarity, the operation of controlling the input current Iin in the negative direction is performed. Here, since the input voltage Vin is a voltage (Vsub), it is controlled to output a voltage (−Vsub) or more opposite to the input voltage Vin from the inverter circuit 100 as in T9, but the input current Iin is controlled in the negative direction. The input voltage Vin does not change.

  T11 is a period in which the AC synchronous sine wave is positive and the short-circuit switch is on. In this period T11, since the current command Iin * is positive, the input current Iin is controlled in the positive direction. Here, since the input voltage Vin is a voltage (Vsub), the inverter circuit 100 performs output control opposite to the input voltage Vin, and the inverter circuit 100 includes a combination of turning off all the semiconductor switch elements 101a to 104a. Control.

  At this time, since the input current Iin is controlled to be positive, the input voltage Vin decreases. Here, if the input voltage Vin decreases and becomes negative, in order to control the input current Iin to positive polarity, the inverter circuit 100 needs to perform output control so as to face the negative input voltage Vin. However, in the case of an output opposite to the input voltage Vin, the inverter circuit 100 is switched by a combination of turning off all the semiconductor switch elements 101a to 104a, and the input current Iin cannot be controlled. Therefore, the input current Iin cannot be controlled when the input voltage Vin becomes 0 V, and the input voltage Vin does not change.

T12 is a period in which the AC synchronous sine wave is positive and the short-circuit switch is off. In this period T12, since the current command Iin * is positive, the input current Iin is controlled in the positive direction. Since the input voltage Vin is 0V, the input current Iin is controlled only by the output voltage of the inverter circuit 100. However, when Vdc> Vsub, the current cannot be controlled and the input voltage Vin does not vary.
If Vdc <Vsub, the current can be controlled by the output voltage of the inverter circuit 100. However, when the positive input current Iin flows, the input voltage Vin becomes negative and the output of the inverter circuit 100 is opposed to the input voltage Vin. Therefore, a combination that turns off each of the semiconductor switch elements 101a to 104a. As a result, the inverter circuit 100 is switched, and as a result, the input voltage Vin is maintained with almost no fluctuation from 0V.

  Note that even when power-off is detected at a timing different from that in FIG. 15, the input voltage Vin is stabilized at 0V. Also, when the condition of | Vin | <Vsub is not satisfied and the short-circuit switch is forcibly turned off, the input voltage Vin is similarly stabilized at 0 V after the power-off is detected.

In the third embodiment, if the power-off detection means 1000 detects the power-off, the switching method in the case where the inverter circuit 100 outputs a voltage so as to face the input voltage Vin is the semiconductor switch of the inverter circuit 100. The elements 101a to 104a are all changed to be turned off, and PWM control is performed. As a result, the input voltage Vin does not fluctuate due to the output of the inverter circuit after the power-off detection is detected, and is stabilized at 0V. As a result, it is possible to prevent accidents such as an electric shock due to a voltage generated between terminals such as a plug connecting the power conversion device to the power source, and an electric shock in the security and maintenance of the power system.

  Further, even if the power-off detection unit 1000 erroneously detects power-off, the inverter circuit 100 is controlled by PWM control including the combination of turning off all the semiconductor switch elements 101a to 104a as described above. Control of the input current Iin having a power factor of approximately 1 can be continued.

When all the semiconductor switch elements 101a to 104a of the inverter circuit 100 are turned off, the input current Iin flows through a path that passes through any two of the diodes 101b to 104b.
Here, when the conduction loss of the diodes 101b to 104b is larger than the conduction loss when the semiconductor switch elements 101a to 104a are turned on, the diodes 101b to 104b are connected only when the power-off detection means detects the power-off. Since the control is conducted intentionally, loss during control of the input current Iin having an input power factor of approximately 1 can be suppressed.

1: AC power supply, 2: Reactor,
3: Smoothing capacitor, 3a, 3b: DC bus,
4: Input filter circuit
10: Control circuit 11, 12: Gate signal 100: Inverter circuit 105: DC voltage source,
101a, 102a, 103a, 104a: semiconductor switch elements,
300: Converter circuit, 301, 303: Diode,
302a, 304a: switches (semiconductor switch elements),
1000: Power-off detection means
t1, t2: first and second input terminals, input voltage Vin,
Iin: input current, Vsub: DC voltage source voltage,
Vdc: smoothing capacitor voltage.

Claims (14)

A first input terminal and a second input terminal connected to a power source;
One or more alternating current sides of a single phase inverter composed of a plurality of semiconductor switch elements and a direct current voltage source are connected in series, and the alternating current side is connected in series to the first input terminal and the output of each single phase inverter. An inverter circuit that superimposes the sum of
One or more switches connected between the DC buses, one AC terminal is connected to the AC output line at the rear stage of the inverter circuit, the other AC terminal is connected to the second input terminal, and the AC A converter circuit connected between the terminals so as to be short-circuited by the switch, and outputting DC power between the DC buses, and
A smoothing capacitor connected between the DC buses and smoothing the output of the converter circuit;
A short-circuit period for bypassing the smoothing capacitor by short-circuiting the AC terminals of the converter circuit, and a control circuit for controlling the inverter circuit using a voltage or current command, the power supply being disconnected A power converter that generates an alternating voltage between the first input terminal and the second input terminal by the output of the inverter circuit ,
The control circuit is disconnected from the power supply when the amount of change in the frequency or period of the voltage generated between the first input terminal and the second input terminal is equal to or greater than a predetermined change threshold. A power conversion device comprising power-off detection means for detecting the power. A first input terminal and a second input terminal connected to a power source;
One or more alternating current sides of a single phase inverter composed of a plurality of semiconductor switch elements and a direct current voltage source are connected in series, and the alternating current side is connected in series to the first input terminal and the output of each single phase inverter. An inverter circuit that superimposes the sum of
One or more switches connected between the DC buses, one AC terminal is connected to the AC output line at the rear stage of the inverter circuit, the other AC terminal is connected to the second input terminal, and the AC A converter circuit connected between the terminals so as to be short-circuited by the switch, and outputting DC power between the DC buses, and
A smoothing capacitor connected between the DC buses and smoothing the output of the converter circuit;
A short-circuit period for bypassing the smoothing capacitor by short-circuiting the AC terminals of the converter circuit, and a control circuit for controlling the inverter circuit using a voltage or current command, the power supply being disconnected A power converter that generates an alternating voltage between the first input terminal and the second input terminal by the output of the inverter circuit,
When the phase difference between the phase of the voltage generated between the first input terminal and the second input terminal and the AC synchronous sine wave or the phase difference integrated value is equal to or greater than a predetermined threshold, the control circuit A power conversion device comprising power-off detection means for detecting that the connection with the device has been disconnected . A first input terminal and a second input terminal connected to a power source;
One or more alternating current sides of a single phase inverter composed of a plurality of semiconductor switch elements and a direct current voltage source are connected in series, and the alternating current side is connected in series to the first input terminal and the output of each single phase inverter. An inverter circuit that superimposes the sum of
One or more switches connected between the DC buses, one AC terminal is connected to the AC output line at the rear stage of the inverter circuit, the other AC terminal is connected to the second input terminal, and the AC A converter circuit connected between the terminals so as to be short-circuited by the switch, and outputting DC power between the DC buses, and
A smoothing capacitor connected between the DC buses and smoothing the output of the converter circuit;
A short-circuit period for bypassing the smoothing capacitor by short-circuiting the AC terminals of the converter circuit, and a control circuit for controlling the inverter circuit using a voltage or current command, the power supply being disconnected A power converter that generates an alternating voltage between the first input terminal and the second input terminal by the output of the inverter circuit,
The control circuit includes power-off detection means for detecting that the connection with the power source is disconnected when the value of the current flowing through the first input terminal or the second input terminal is less than a predetermined current threshold. A power conversion device comprising: A first input terminal and a second input terminal connected to a power source;
One or more alternating current sides of a single phase inverter composed of a plurality of semiconductor switch elements and a direct current voltage source are connected in series, and the alternating current side is connected in series to the first input terminal and the output of each single phase inverter. An inverter circuit that superimposes the sum of
One or more switches connected between the DC buses, one AC terminal is connected to the AC output line at the rear stage of the inverter circuit, the other AC terminal is connected to the second input terminal, and the AC A converter circuit connected between the terminals so as to be short-circuited by the switch, and outputting DC power between the DC buses, and
A smoothing capacitor connected between the DC buses and smoothing the output of the converter circuit;
A short-circuit period for bypassing the smoothing capacitor by short-circuiting the AC terminals of the converter circuit, and a control circuit for controlling the inverter circuit using a voltage or current command, the power supply being disconnected A power converter that generates an alternating voltage between the first input terminal and the second input terminal by the output of the inverter circuit,
In the control circuit, a voltage generated between the first input terminal and the second input terminal and an effective value of the voltage are equal to or lower than a predetermined voltage threshold value, or between the first input terminal and the second input terminal. A power converter comprising: a power-off detection means for detecting that the connection with the power source is disconnected when an effective value change amount of a voltage generated therebetween is equal to or greater than a predetermined voltage effective value threshold value . A first input terminal and a second input terminal connected to a power source;
One or more alternating current sides of a single phase inverter composed of a plurality of semiconductor switch elements and a direct current voltage source are connected in series, and the alternating current side is connected in series to the first input terminal and the output of each single phase inverter. An inverter circuit that superimposes the sum of
One or more switches connected between the DC buses, one AC terminal is connected to the AC output line at the rear stage of the inverter circuit, the other AC terminal is connected to the second input terminal, and the AC A converter circuit connected between the terminals so as to be short-circuited by the switch, and outputting DC power between the DC buses, and
A smoothing capacitor connected between the DC buses and smoothing the output of the converter circuit;
A short-circuit period for bypassing the smoothing capacitor by short-circuiting the AC terminals of the converter circuit, and a control circuit for controlling the inverter circuit using a voltage or current command, the power supply being disconnected A power converter that generates an alternating voltage between the first input terminal and the second input terminal by the output of the inverter circuit,
The control circuit is configured such that power input from the first input terminal and the second input terminal is equal to or lower than a predetermined threshold value, or predetermined power input from the first input terminal and the second input terminal. A power conversion device comprising: a power-off detection means for detecting that the connection with the power source has been disconnected when the amount of decrease within a period is equal to or greater than a predetermined decrease amount threshold . A first input terminal and a second input terminal connected to a power source;
One or more alternating current sides of a single phase inverter composed of a plurality of semiconductor switch elements and a direct current voltage source are connected in series, and the alternating current side is connected in series to the first input terminal and the output of each single phase inverter. An inverter circuit that superimposes the sum of
One or more switches connected between the DC buses, one AC terminal is connected to the AC output line at the rear stage of the inverter circuit, the other AC terminal is connected to the second input terminal, and the AC A converter circuit connected between the terminals so as to be short-circuited by the switch, and outputting DC power between the DC buses, and
A smoothing capacitor connected between the DC buses and smoothing the output of the converter circuit;
A short-circuit period for bypassing the smoothing capacitor by short-circuiting the AC terminals of the converter circuit, and a control circuit for controlling the inverter circuit using a voltage or current command, the power supply being disconnected A power converter that generates an alternating voltage between the first input terminal and the second input terminal by the output of the inverter circuit,
The control circuit is disconnected from the power supply when the voltage of the smoothing capacitor is equal to or lower than a predetermined threshold, or when the amount of decrease in the voltage of the smoothing capacitor within a predetermined period is equal to or greater than a predetermined decrease amount threshold. A power conversion device comprising power-off detection means for detecting this . A first input terminal and a second input terminal connected to a power source;
One or more alternating current sides of a single phase inverter composed of a plurality of semiconductor switch elements and a direct current voltage source are connected in series, and the alternating current side is connected in series to the first input terminal and the output of each single phase inverter. An inverter circuit that superimposes the sum of
One or more switches connected between the DC buses, one AC terminal is connected to the AC output line at the rear stage of the inverter circuit, the other AC terminal is connected to the second input terminal, and the AC A converter circuit connected between the terminals so as to be short-circuited by the switch, and outputting DC power between the DC buses, and
A smoothing capacitor connected between the DC buses and smoothing the output of the converter circuit;
A short-circuit period for bypassing the smoothing capacitor by short-circuiting the AC terminals of the converter circuit, and a control circuit for controlling the inverter circuit using a voltage or current command, the power supply being disconnected A power converter that generates an alternating voltage between the first input terminal and the second input terminal by the output of the inverter circuit,
When the current output from the converter circuit is equal to or less than a predetermined threshold, or the amount of decrease in the current output from the converter circuit within a predetermined period is equal to or greater than a predetermined decrease amount threshold, the control circuit A power conversion device comprising power-off detection means for detecting disconnection . A first input terminal and a second input terminal connected to a power source;
One or more alternating current sides of a single phase inverter composed of a plurality of semiconductor switch elements and a direct current voltage source are connected in series, and the alternating current side is connected in series to the first input terminal and the output of each single phase inverter. An inverter circuit that superimposes the sum of
One or more switches connected between the DC buses, one AC terminal is connected to the AC output line at the rear stage of the inverter circuit, the other AC terminal is connected to the second input terminal, and the AC A converter circuit connected between the terminals so as to be short-circuited by the switch, and outputting DC power between the DC buses, and
A smoothing capacitor connected between the DC buses and smoothing the output of the converter circuit;
A short-circuit period for bypassing the smoothing capacitor by short-circuiting the AC terminals of the converter circuit, and a control circuit for controlling the inverter circuit using a voltage or current command, the power supply being disconnected A power converter that generates an alternating voltage between the first input terminal and the second input terminal by the output of the inverter circuit,
When the voltage of the DC voltage source of the single-phase inverter is equal to or lower than a predetermined threshold, or the amount of decrease in the voltage of the DC voltage source of the single-phase inverter is equal to or greater than a predetermined decrease amount threshold In addition, the power conversion device further comprises power-off detection means for detecting that the connection with the power source has been disconnected . A first input terminal and a second input terminal connected to a power source;
One or more alternating current sides of a single phase inverter composed of a plurality of semiconductor switch elements and a direct current voltage source are connected in series, and the alternating current side is connected in series to the first input terminal and the output of each single phase inverter. An inverter circuit that superimposes the sum of
One or more switches connected between the DC buses, one AC terminal is connected to the AC output line at the rear stage of the inverter circuit, the other AC terminal is connected to the second input terminal, and the AC A converter circuit connected between the terminals so as to be short-circuited by the switch, and outputting DC power between the DC buses, and
A smoothing capacitor connected between the DC buses and smoothing the output of the converter circuit;
A short-circuit period for bypassing the smoothing capacitor by short-circuiting the AC terminals of the converter circuit, and a control circuit for controlling the inverter circuit using a voltage or current command, the power supply being disconnected A power converter that generates an alternating voltage between the first input terminal and the second input terminal by the output of the inverter circuit,
The control circuit includes power-off detection means for detecting that the connection with the power source is disconnected when a current flowing through the DC voltage source of the single-phase inverter is less than a predetermined current threshold. A power converter. The control circuit combines a plurality of power-off detection means according to any one of claims 1 to 9, and detects that the connection of the power source has been disconnected based on the plurality of power-off detection means . Power conversion device. The control circuit detects the disconnection of the power supply by the power-off detecting means, electric power conversion according to any one of claims 1 to 10 to stop the control and all off the switch and the semiconductor switch element apparatus. The control circuit detects the power-off by the power-off detection means, and when a voltage value generated between the first input terminal and the second input terminal becomes a predetermined threshold value or less, The power converter according to any one of claims 1 to 10 , wherein control is stopped by turning off all of the semiconductor switch elements and the switches. When the control circuit detects the power-off detection by the power-off detection means, each single-phase inverter outputs a voltage opposite to the voltage generated between the first input terminal and the second input terminal. In this case, the power conversion device according to any one of claims 1 to 10 , wherein the switching control method is changed so as to turn off all of the plurality of semiconductor switch elements constituting the single-phase inverter. The converter circuit is configured by connecting two bridge circuits each composed of a diode and a semiconductor switch element as a switch connected in series between the DC buses in parallel, and each semiconductor switch element has a diode in antiparallel. The power converter of any one of Claims 1 thru | or 13 connected.

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