JP2012143049A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized power conversion device that reduces rush current and discharges charges accumulated in a smoothing capacitor and a DC voltage source.SOLUTION: A power conversion device comprises: an inverter circuit constituted by a single-phase inverter having a plurality of semiconductor switching elements and a DC voltage source, or a plurality of the single-phase inverters whose AC sides are series connected; a smoothing capacitor whose one end is connected to the subsequent stage of the inverter circuit via a rectifier diode; and a short-circuit switch whose one end is connected to the output of the inverter circuit and whose the other end is connected to the other end of the smoothing capacitor. The power conversion device further comprises: a rush-current prevention circuit; a discharging switch that is interposed between the rush-current prevention circuit and the smoothing capacitor, and connects and disconnects the smoothing capacitor and the input of the rush-current prevention circuit; and a controller that turns on or off the semiconductor switching element, the short-circuit switch, and the discharging switch.

Description

  The present invention includes an inrush current prevention circuit for preventing an inrush current flowing from a power supply device of a power conversion device that includes a circuit for improving an input power factor to convert alternating current power into direct current power, and an electric charge accumulated in an internal capacitor. It is related with the discharge circuit which discharges.

  A conventional power conversion device has an inverter circuit in which one or more single-phase inverters are connected in series in a subsequent stage after rectifying an AC input, and is provided with a smoothing capacitor and a short-circuit switch via a rectifier diode in the subsequent stage. Is an input power factor that controls the output of the inverter circuit using a current command so that the smoothing capacitor DC voltage follows the target voltage and improves the input power factor so that it is turned on only in the short-circuit phase range centered on the zero-cross phase. Improvement, reduction of power loss and noise (for example, see Patent Document 1).

JP 2009-95160 A

  However, the above-described conventional power conversion device has to be provided with a resistor for preventing inrush current at the start of operation and a discharge resistor for discharging the charge stored in the smoothing capacitor at the end of operation. It was. Each resistor is expensive and is not used because it is not used during normal operation. For this reason, there existed a problem that a power converter device enlarged and manufacturing cost became high.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a small-sized power conversion device that reduces inrush current and discharges electric charges stored in a smoothing capacitor and a DC voltage source. And

  A power conversion device according to the present invention includes a single-phase inverter having a plurality of semiconductor switch elements and a DC voltage source, or an inverter circuit composed of a plurality of the single-phase inverters connected in series on the AC side, and the inverter circuit A smoothing capacitor having one end connected to the latter stage via a rectifier diode and a shorting switch having one end connected to the output of the inverter circuit and the other end connected to the other end of the smoothing capacitor In the power conversion device, for discharging, the inrush current prevention circuit is interposed between the smoothing capacitor and the input of the inrush current prevention circuit, and connects and separates the smoothing capacitor and the input of the inrush current prevention circuit. A switch, and a control unit that turns on and off the semiconductor switch element, the short-circuit switch, and the discharge switch. That.

  The power conversion device according to the present invention can reduce the inrush current and discharge the smoothing capacitor and the DC voltage source with one resistor, and can prevent the device from being scaled up and costing up.

It is a block diagram of the power converter device which concerns on Embodiment 1 of this invention. It is a figure which shows an example of the path | route into which a charging current flows immediately after an operation | movement start with the power converter device which concerns on Embodiment 1 of this invention. It is a figure which shows the path | route of the electric current which flows when a smoothing capacitor is discharged with the power converter device which concerns on Embodiment 1 of this invention. It is a figure which shows the path | route of the electric current which flows when discharging a DC voltage source with the power converter device which concerns on Embodiment 1 of this invention. It is a flowchart which shows the switching determination algorithm of the discharge path which concerns on Embodiment 1 of this invention. It is a block diagram of the other power converter device which concerns on Embodiment 1 of this invention. It is a block diagram of the power converter device which concerns on Embodiment 2 of this invention. It is a figure which shows the path | route of the electric current which flows when a smoothing capacitor is discharged with the power converter device which concerns on Embodiment 2 of this invention. It is a figure which shows the path | route of the electric current which flows when discharging a DC voltage source with the power converter device which concerns on Embodiment 2 of this invention. It is a block diagram of the other power converter device which concerns on Embodiment 2 of this invention. It is a block diagram of the power converter device which concerns on Embodiment 3 of this invention. It is a figure which shows an example of the path | route into which a charging current flows immediately after an operation | movement start with the power converter device which concerns on Embodiment 3 of this invention. It is a figure which shows the path | route of the electric current which flows when a smoothing capacitor is discharged with the power converter device which concerns on Embodiment 3 of this invention. It is a figure which shows the path | route of the electric current which flows when a DC voltage source is discharged with the power converter device which concerns on Embodiment 3 of this invention.

Hereinafter, preferred embodiments of a power conversion device of the present invention will be described with reference to the drawings.
Embodiment 1 FIG.
1 is a configuration diagram of a power converter according to Embodiment 1 of the present invention.
As shown in FIG. 1, the power conversion device according to Embodiment 1 of the present invention is a main relay (hereinafter referred to as an AC voltage power source) (hereinafter referred to as an AC power source) 1 serving as an AC input power source. This is composed of elements from 2 to the smoothing capacitor 22. When the smoothing capacitor 22 is viewed from the main relay 2, the front stage is referred to as a front stage, and when it is disposed on the opposite side, the rear stage is referred to. That is, the smoothing capacitor 22 is disposed at the most downstream stage.
The main relay 2 is connected to the input of a diode bridge 12 as a rectifier circuit. The output of the diode bridge 12 is connected in series in the order of the inrush current prevention circuit 7, the rectification current detection circuit 31, and the reactor 13 as a current limiting circuit.
The inrush current prevention circuit 7 includes an inrush current prevention resistor 5 and a relay (hereinafter referred to as a charging relay) 4 connected in parallel to the inrush current prevention resistor 5.

  The output of the reactor 13 is connected in series to the AC side of the inverter circuit 14 configured by a single-phase inverter. The single-phase inverter constituting the inverter circuit 14 includes a semiconductor switch element 17 formed of a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) in which diodes are connected in antiparallel and a diode 15 connected in series with the semiconductor switch element 17. And a series circuit constituted by the semiconductor switch element 18 and the diode 16 connected in series with the semiconductor switch element 18 are constituted by a bridge circuit connected in parallel. A semiconductor switch element 17 is connected to the anode of the diode 15, and a semiconductor switch element 18 is connected to the cathode of the diode 16.

The output of the reactor 13 is connected to the connection point between the semiconductor switch element 17 and the diode 15, and the connection point between the semiconductor switch element 18 and the diode 16 is the output.
A DC voltage source 19 and a DC voltage source voltage detection circuit 32 are connected in parallel between the connection point of the cathode of the diode 15 and the semiconductor switch element 18 and the connection point of the anode of the diode 16 and the semiconductor switch element 17.
The reactor 13 may be connected in series to the subsequent stage of the inverter circuit 14.

The short circuit switch 21 and the rectifier diode 20 are connected in parallel to the output of the inverter circuit 14, and the cathode of the rectifier diode 20 is connected to the positive electrode of the smoothing capacitor 22 in the output stage. Here, the connection point between the short-circuit switch 21 and the anode of the rectifier diode 20 is connected to the AC output line at the subsequent stage of the inverter circuit 14, and the other end of the short-circuit switch 21 is connected to the negative electrode of the smoothing capacitor 22.
A smoothing capacitor voltage detection circuit 33 is connected in parallel to the smoothing capacitor 22.
In addition, a discharge relay (hereinafter referred to as a discharge relay) 3 that connects and separates the positive electrode of the smoothing capacitor 22 and the output of the diode bridge 12 is provided.

The control unit 6 is connected to the main relay 2, the charge relay 4, the discharge relay 3, the semiconductor switch elements 17 and 18, and the short-circuit switch 21 through control lines 40a, 40b, 40c, 40d, 40e, and 40f, respectively. The relay 2, the charging relay 4, the discharging relay 3, the semiconductor switch elements 17 and 18, and the shorting switch 21 are controlled to be turned on / off.
The control unit 6 is connected to the rectified current detection circuit 31, the DC voltage source voltage detection circuit 32, and the smoothing capacitor voltage detection circuit 33 through signal lines 41a, 41b, and 41c, respectively. A detected value of current or voltage is acquired from the source voltage detection circuit 32 and the smoothing capacitor voltage detection circuit 33.
In addition, although the short circuit switch 21 is illustrated as a semiconductor switch element in which a diode is connected in antiparallel, the present invention is not limited to this and may be a mechanical switch or the like.

The operation of the power conversion device configured as described above will be described. First, the operation during charging will be described.
FIG. 2 is a configuration diagram overwriting an example of a path through which a current flows in the power conversion apparatus according to Embodiment 1 of the present invention immediately after the start of operation.
At the start of operation, immediately after the main relay 2 is turned on and the AC power source 1 is turned on with the charging relay 4 turned off, the AC power source 1, the main relay 2, the diode bridge 12, and the inrush are sequentially entered as shown in FIG. Inrush current flows through the path of the current prevention resistor 5 and the reactor 13, and the inrush current prevention resistor 5 reduces the inrush current. FIG. 2 shows a path through which the charging current flows when the inrush current is reduced. However, the path is not limited to this path.
Thereafter, when the charging relay 4 is turned on, the path through which the inrush current flows is changed to the path of the AC power source 1, the main relay 2, the diode bridge 12, the charging relay 4, and the reactor 13.

Next, the operation during discharging will be described.
When the main relay 2 is turned off and the AC power supply 1 is disconnected from the power conversion device, the discharge relay 3 is turned on and the charging relay 4 is turned off to start discharging the DC voltage source 19 and the smoothing capacitor 22.
However, it is not preferable to discharge the DC voltage source 19 and the smoothing capacitor 22 simultaneously. The reason is that if the DC voltage source 19 and the smoothing capacitor 22 are discharged at the same time, a large amount of power is applied to the inrush current prevention resistor 5, so that the inrush current prevention resistor 5 must have a rating that can withstand it. This is because the inrush current preventing resistor 5 has a demerit that it is large and costly. Further, for example, when a voltage equal to or higher than the rated voltage of the DC voltage source 19 is applied to the smoothing capacitor 22, if discharged simultaneously, the voltage of the smoothing capacitor 22 is applied to the DC voltage source 19, and the DC voltage source 19 and surrounding elements are overrated. This is because there is a possibility of breaking, and in order to avoid it, it is necessary to raise the rating after all, and there is a demerit that it becomes larger. In order to solve this problem, the semiconductor switch elements 17 and 18 and the short-circuit switch 21 are controlled, and the DC voltage source 19 and the smoothing capacitor 22 are separately discharged, thereby reducing the size of the inrush current preventing resistor 5. Plan.

FIG. 3 is a configuration diagram overwriting a path in which the electric charge charged in the smoothing capacitor 22 immediately after the start of discharge flows to the power conversion device according to the first embodiment of the present invention.
First, the main relay 2 and the charge relay 4 are turned off, the discharge relay 3 is turned on, the semiconductor switch element 17 is turned on, the semiconductor switch element 18 is turned off, and the short-circuit switch 21 is turned on. As shown in FIG. 3, the electric charge charged in the smoothing capacitor 22 is the smoothing capacitor 22 (positive electrode), the discharge relay 3, the inrush current preventing resistor 5, the reactor 13, the semiconductor switch element 17, the diode 16, the shorting switch 21, the smoothing. The smoothing capacitor 22 is discharged through a path configured in the order of the capacitor 22 (negative electrode) (hereinafter referred to as a first discharge path).

  FIG. 4 shows the discharge path when the semiconductor switch element 17 is turned on and the semiconductor switch element 18 is turned off. When the semiconductor switch element 17 is turned off and the semiconductor switch element 18 is turned on, the smoothing capacitor 22 ( Positive electrode), discharge relay 3, inrush current prevention resistor 5, reactor 13, diode 15, semiconductor switch element 18, short-circuit switch 21, smoothing capacitor 22 (negative electrode) in the order of discharge, the charge of smoothing capacitor 22 is discharged. Is done.

FIG. 4 is a configuration diagram overwriting a path in which the electric charge charged in DC voltage source 19 flows to the power conversion device according to Embodiment 1 of the present invention.
Next, the main relay 2 and the charging relay 4 are turned off, the discharge relay 3 is turned on, the semiconductor switch elements 17 and 18 are turned on, and the shorting switch 21 is turned off, as shown in FIG. The charges charged in the DC voltage source 19 are the DC voltage source 19 (positive electrode), the semiconductor switch element 18, the rectifier diode 20, the discharge relay 3, the inrush current preventing resistor 5, the reactor 13, the semiconductor switch element 17, and the DC voltage source. It flows through a path (hereinafter referred to as a second discharge path) in the order of 19 (negative electrode), and the DC voltage source 19 is discharged.

FIG. 5 is a flowchart showing a discharge path switching determination algorithm executed in the control unit 6.
The switching determination algorithm of the control unit 6 first determines in step S1 whether or not the voltage of the smoothing capacitor 22 is equal to or higher than the voltage of the DC voltage source 19, and when the voltage of the smoothing capacitor 22 is equal to or higher than the voltage of the DC voltage source 19. Proceeds to step S2, and when the voltage of the smoothing capacitor 22 is less than the voltage of the DC voltage source 19, the process proceeds to step S7.
In step S2, the first discharge path is set valid and the second discharge path is set invalid, the main relay 2 and the charge relay 4 are turned off, the discharge relay 3 is turned on, the semiconductor switch element 17 is turned on, The semiconductor switch element 18 is turned off, the shorting switch 21 is turned on, and the discharge of the smoothing capacitor 22 is started.
In step S3, it is determined whether or not the voltage of the smoothing capacitor 22 is equal to or higher than the threshold value Vth. When it is determined that the voltage of the smoothing capacitor 22 is equal to or higher than the threshold value Vth, step S3 is repeated, and the voltage of the smoothing capacitor 22 is determined to be less than the threshold value Vth. If yes, go to Step S4.

In step S4, the first discharge path is disabled and the second discharge path is enabled, the main relay 2 and the charge relay 4 are turned off, the discharge relay 3 is turned on, and the semiconductor switch elements 17 and 18 are turned on, respectively. The switch is turned on, the short-circuit switch 21 is turned off, and the discharge of the DC voltage source 19 is started.
In step S5, it is determined whether or not the voltage of the DC voltage source 19 is equal to or higher than the threshold value Vth. If the voltage of the DC voltage source 19 is equal to or higher than the threshold value Vth, step S5 is repeated, and the voltage of the DC voltage source 19 is lower than the threshold value Vth. The process proceeds to step S6.
In step S6, the first discharge path and the second discharge path are invalidated, the discharge relay 3 and the semiconductor switch elements 17 and 18 are turned off, and the discharge operation is finished.

In step S7, the first discharge path is set to be invalid and the second discharge path is set to be valid, the main relay 2 and the charge relay 4 are turned off, the discharge relay 3 is turned on, and the semiconductor switch elements 17 and 18 are turned on. The switch is turned on, the short-circuit switch 21 is turned off, and the discharge of the DC voltage source 19 is started.
In Step S8, it is determined whether or not the voltage of the DC voltage source 19 is equal to or higher than the threshold value Vth. If the voltage of the DC voltage source 19 is equal to or higher than the threshold value Vth, Step S8 is repeated, and the voltage of the DC voltage source 19 is lower than the threshold value Vth. The process proceeds to step S9.

In step S9, the first discharge path is set valid and the second discharge path is set invalid, the main relay 2 and the charge relay 4 are turned off, the discharge relay 3 is turned on, the semiconductor switch element 17 is turned on, The semiconductor switch element 18 is turned off, the shorting switch 21 is turned on, and the discharge of the smoothing capacitor 22 is started.
In step S10, it is determined whether or not the voltage of the smoothing capacitor 22 is equal to or higher than the threshold value Vth. When it is determined that the voltage of the smoothing capacitor 22 is equal to or higher than the threshold value Vth, step S10 is repeated and the voltage of the smoothing capacitor 22 is determined to be less than the threshold value Vth. If yes, go to Step S6.

  Note that the switching determination algorithm executed in the control unit 6 is a flowchart in the case where the voltage value is the threshold value, but is not limited thereto, and for example, the switching determination may be performed using the current value as the threshold value.

  Further, in the power conversion device according to the first embodiment described above, the inrush current prevention circuit 7 is connected in series to the output of the diode bridge 12, but the present invention is not limited to this, the rear stage of the reactor 13, the inverter circuit 14 It may be connected to the subsequent stage or the subsequent stage of the main relay 2.

In the power conversion device according to the first embodiment described above, the cathode of the rectifier diode 20 is connected to the positive electrode of the smoothing capacitor 22 at the output stage, but the anode of the rectifier diode 20 is connected to the negative electrode of the smoothing capacitor 22. The same operation as in the first embodiment may be obtained.
In addition, the inverter circuit 14 is configured by one single-phase inverter. However, as shown in FIG. 6, a plurality of single-phase inverters 14a and 14b are connected in series to form an inverter circuit 100. May be. At this time, the inrush current prevention circuit 7 may be connected in series between the single-phase inverter 14a and the single-phase inverter 14b.

Embodiment 2. FIG.
FIG. 7 is a configuration diagram of a power conversion apparatus according to Embodiment 2 of the present invention.
The power conversion device according to the second embodiment of the present invention differs from the power conversion device according to the first embodiment of the present invention in the arrangement position of the short-circuit switch 21a, and the other portions are the same. Is added and explanation is omitted.
In the power conversion device according to Embodiment 2 of the present invention, a short-circuit switch 21 a is interposed between the negative electrode of the DC voltage source 19 and the negative electrode of the smoothing capacitor 22 constituting the inverter circuit 14. That is, one end of the shorting switch 21 a is connected to the negative electrode of the DC voltage source 19, and the other end of the shorting switch 21 a is connected to one end of the diode bridge 12.

FIG. 8 is a configuration diagram overwriting a path in which the electric charge charged in the smoothing capacitor 22 flows to the power conversion device according to the second embodiment of the present invention.
When discharging the smoothing capacitor 22, the main relay 2 and the charging relay 4 are turned off, the discharge relay 3 is turned on, the semiconductor switch element 17 is turned on, the semiconductor switch element 18 is turned off, and the shorting switch 21a is turned on. Thus, as shown by a thick solid line in FIG. 8, the positive electrode of the smoothing capacitor 22, the discharge relay 3, the inrush current prevention resistor 5, the reactor 13, the semiconductor switch element 17, the shorting switch 21 a, and the negative electrode of the smoothing capacitor 22 are configured. The electric charge charged in the smoothing capacitor 22 flows through the discharge path.

FIG. 9 is a configuration diagram overwriting a path in which the electric charge charged in DC voltage source 19 flows to the power conversion device according to Embodiment 2 of the present invention.
When discharging the DC voltage source 19, the main relay 2 and the charging relay 4 are turned off, the discharge relay 3 is turned on, the semiconductor switch element 17 and the semiconductor switch element 18 are turned on, and the shorting switch 21a is turned off. 9, the positive electrode of the DC voltage source 19, the semiconductor switch element 18, the rectifier diode 20, the discharge relay 3, the inrush current prevention resistor 5, the reactor 13, the semiconductor switch element 17, and the DC voltage source 19, as shown by a thick solid line in FIG. The electric charge charged in the DC voltage source 19 flows through the discharge path constituted by the negative electrode.

  The power conversion device according to the second embodiment of the present invention has the same effect as the power conversion device according to the first embodiment of the present invention, and the shorting switch 21a is connected to the negative electrode of the DC voltage source 19, so that the smoothing The number of elements through which current flows when the capacitor 22 is discharged is reduced, and the burden on the elements during discharge can be reduced. In addition, the power conversion device can reduce the conduction loss, and as a result, the conversion efficiency of the entire power conversion device can be improved.

As shown in FIG. 10, when the inverter circuit 100 is configured by connecting a plurality of single-phase inverters 14a and 14b in series, the last one of the plurality of single-phase inverters 14a and 14b is connected. By connecting the short-circuit switch 21a to the negative electrode of the DC voltage source 19 of the single-phase inverter 14b, the same operation can be achieved.
Also in this embodiment, the inrush current prevention circuit 7 is connected in series to the output stage of the diode bridge 12, but the present invention is not limited to this, and is connected in series between the single-phase inverters 14a and 14b. May be.

Embodiment 3 FIG.
FIG. 11 is a configuration diagram of a power conversion apparatus according to Embodiment 3 of the present invention.
As shown in FIG. 11, in the power converter according to Embodiment 3 of the present invention, the first terminal of the AC power supply 1 is connected to one end of the main relay 2, and the other end of the main relay 2 is the inrush current prevention resistor. 5 and the charging relay 4 are connected to the input of an inrush current prevention circuit 7. The output of the inrush current preventing circuit 7 is connected to the rectified current detecting circuit 31, and the rectified current detecting circuit 31 is connected to the reactor 13.
Reactor 13 is connected in series to the AC side of inverter circuit 29 configured by a single-phase inverter.

  The single-phase inverter constituting the inverter circuit 29 includes an IGBT (Insulated Gate Bipolar Transistor) in which diodes are connected in antiparallel, a MOSFET having a diode interposed between a source and a drain, and a semiconductor switch element 17. 27 is composed of a bridge circuit in which a series circuit in which 27 is connected in series and a series circuit in which the semiconductor switch element 18 and the semiconductor switch element 28 are connected in series are connected in parallel. The semiconductor switch element 17 is connected to the source of the semiconductor switch element 27, and the semiconductor switch element 18 is connected to the drain of the semiconductor switch element 28.

The output of the reactor 13 is connected to the connection point between the semiconductor switch element 17 and the semiconductor switch element 27, and the connection point between the semiconductor switch element 18 and the semiconductor switch element 28 is the output.
A DC voltage source 19 and a DC voltage source voltage detection circuit 32 are connected in parallel between a connection point between the semiconductor switch element 27 and the semiconductor switch element 18 and a connection point between the semiconductor switch element 28 and the semiconductor switch element 17.

A first series circuit 26a in which a short-circuit switch 23a made of a semiconductor switch element and a rectifier diode 24a are connected in series, and a second short-circuit switch 23b made of a semiconductor switch element and a rectifier diode 24b are connected in series. Are connected in parallel to form a bridge circuit.
The output of the inverter circuit 29 is connected to the connection point between the short-circuit switch 23a and the rectifier diode 24a. A second terminal of the AC power supply 1 is connected to a connection point between the short-circuit switch 23b and the rectifier diode 24b.
The positive electrode of the smoothing capacitor 22 is connected to the connection point between the rectifier diode 24a and the rectifier diode 24b, and the negative electrode of the smoothing capacitor 22 is connected to the connection point between the short-circuit switch 23a and the short-circuit switch 23b.
A smoothing capacitor voltage detection circuit 33 is connected in parallel to the smoothing capacitor 22.
The short-circuit switches 23a and 23b are not limited to semiconductor switch elements, but may be mechanical switches or the like, and diodes 25a and 25b are connected in antiparallel.

FIG. 12 is a configuration diagram overwriting an example of a path through which a current flows in the power conversion apparatus according to Embodiment 3 of the present invention immediately after the start of operation.
At the start of operation, both the charge relay 4 and the discharge relay 3 are turned off, the semiconductor switch elements 27 and 28 are turned on, the semiconductor switch elements 17 and 18 are turned off, the shorting switch 23b is turned on, and the shorting switch 23a is turned off. Immediately after the main relay 2 is turned on and the AC power source 1 is turned on, the AC power source 1, the main relay 2, the inrush current prevention resistor 5, the reactor 13, and the semiconductor switch element are sequentially shown as a thick solid line in FIG. 27, the DC voltage source 19, the semiconductor switch element 28, the rectifier diode 24a, the smoothing capacitor 22, the shorting switch 23b, and the inrush current flow through the path of the AC power source 1, and the DC voltage source 19 and the smoothing capacitor 22 are charged. The inrush current preventing resistor 5 reduces the inrush current. FIG. 12 shows a path through which the charging current flows when the inrush current is reduced. However, the path is not limited to this path.
Thereafter, when the charging relay 4 is turned on, the semiconductor switch element 27 is turned off, the semiconductor switch element 17 is turned on, and the shorting switch 23a is turned on, the path through which the current flows from the AC power supply 1 is the AC power supply 1, the main relay 2, The charging relay 4, the reactor 13, the semiconductor switch element 17, the semiconductor switch element 28, the short-circuit switch 23a, the short-circuit switch 23b, and the AC power source 1 are changed.

FIG. 13 is a configuration diagram overwriting a path in which the electric charge charged in the smoothing capacitor 22 flows in the power conversion device according to the third embodiment of the present invention.
First, the main relay 2 and the charge relay 4 are turned off, the discharge relay 3 is turned on, the semiconductor switch elements 17 and 28 are turned on, the semiconductor switch elements 18 and 27 are turned off, and the short-circuit switch 23a is turned on. By turning off the short-circuit switch 23b, as shown by a thick solid line in FIG. 13, the electric charge charged in the smoothing capacitor 22 is changed to the smoothing capacitor 22 (positive electrode), the discharge relay 3, the inrush current preventing resistor 5, and the reactor 13. , The semiconductor switch element 17, the semiconductor switch element 28, the short-circuit switch 23 a, and the smoothing capacitor 22 (negative electrode) in this order (hereinafter referred to as a third discharge path) flow to discharge the smoothing capacitor 22.

FIG. 14 is a configuration diagram overwriting a path in which the electric charge charged in DC voltage source 19 flows in the power conversion device according to Embodiment 3 of the present invention.
Next, the main relay 2 and the charge relay 4 are turned off, the discharge relay 3 is turned on, the semiconductor switch elements 17 and 18 are turned on, the semiconductor switch elements 27 and 28 are turned off, and the short-circuit switches 23a and 23b. As shown by a thick solid line in FIG. 14, the electric charge charged in the DC voltage source 19 is changed into the DC voltage source 19 (positive electrode), the semiconductor switch element 18, the rectifier diode 24 a, the discharge relay 3, and the inrush. The current prevention resistor 5, the reactor 13, the semiconductor switch element 17, and the DC voltage source 19 (negative electrode) flow in this order (hereinafter referred to as a fourth discharge path) to discharge the DC voltage source 19.

In the third embodiment, the same effect as in the first embodiment can be obtained, and further, the diode bridge 12 used in the first embodiment is not necessary, so that the number of parts can be reduced and the device configuration is simplified. Become.
In addition, since the number of elements through which current passes can be reduced, conduction loss can be reduced, and the conversion efficiency of the entire power conversion device can be improved.

Also in the third embodiment, as shown in FIG. 7 in relation to the first embodiment, the inverter circuit 100 may be configured by connecting the AC sides of a plurality of single-phase inverters in series. Moreover, in the said embodiment, although the end of the discharge relay 3 is connected to the positive electrode side of the smoothing capacitor 22, it is not restricted to this, You may connect to the negative electrode side of the smoothing capacitor 22.
Also in this embodiment, the charging relay 4 and the inrush current prevention resistor 5 are connected in series to the output stage of the diode bridge 12, but the present invention is not limited to this, and is not limited to the single-phase inverters 14a and 14b. They may be connected in series.

  In the first to third embodiments described above, the rectifier diodes 20, 24a, and 24b are connected to the smoothing capacitor 22. However, instead of these rectifier diodes, a semiconductor switch element is connected, and the same operation is performed by on / off control. You may let them.

  Moreover, in each said embodiment, although the end of the discharge relay 3 is connected to the positive electrode side of the smoothing capacitor 22, it is not restricted to this, You may connect to the negative electrode side of the smoothing capacitor 22.

In each of the above-described embodiments, the changeover switch for connecting and blocking the path uses a relay. However, the present invention is not limited to this. For example, a semiconductor switch element such as a MOSFET or IGBT may be used.

  Similarly, in each of the above embodiments, the inrush current prevention circuit 7 is constituted by a resistor and a relay, but it is not necessary to be a relay, and may be a semiconductor switching element such as a MOSFET or an IGBT, for example.

  1 AC power supply, 2 main relay, 3 discharge relay, 4 charging relay, 5 inrush current prevention resistor, 6 control unit, 7 inrush current prevention circuit, 12 diode bridge, 13 reactor, 14, 29, 100 inverter circuit, 14a, 14b Single-phase inverter, 15, 16, 25a, 25b Diode, 17, 18, 27, 28 Semiconductor switch element, 19 DC voltage source, 20, 24a, 24b Rectifier diode, 21, 23a, 23b Short-circuit switch, 22 Smoothing capacitor, 26a, 26b Series circuit, 31 Rectified current detection circuit, 32 DC voltage source voltage detection circuit, 33 Smoothing capacitor voltage detection circuit, 40a, 40b, 40c, 40d, 40e, 40f Control line, 41a, 41b, 41c Signal line.

Claims (11)

A single-phase inverter having a plurality of semiconductor switch elements and a DC voltage source or an inverter circuit composed of a plurality of the single-phase inverters connected in series on the AC side;
A smoothing capacitor having one end connected via a rectifier diode to the subsequent stage of the inverter circuit;
In a power converter comprising: a shorting switch having one end connected to the output of the inverter circuit and the other end connected to the other end of the smoothing capacitor;
An inrush current prevention circuit,
A discharge switch interposed between the smoothing capacitor and the input of the inrush current prevention circuit, and connecting and separating the smoothing capacitor and the input of the inrush current prevention circuit;
A control unit for turning on and off the semiconductor switch element, the shorting switch, and the discharging switch;
A power conversion device comprising: A single-phase inverter having a plurality of semiconductor switch elements and a DC voltage source or an inverter circuit composed of a plurality of the single-phase inverters connected in series on the AC side;
A smoothing capacitor having one end connected via a rectifier diode to the subsequent stage of the inverter circuit;
In a power converter comprising: a short-circuit switch having one end connected to the negative electrode of the DC voltage source and the other end connected to the other end of the smoothing capacitor;
An inrush current prevention circuit,
A discharge switch interposed between the smoothing capacitor and the input of the inrush current prevention circuit, and connecting and separating the smoothing capacitor and the input of the inrush current prevention circuit;
A control unit for turning on and off the semiconductor switch element, the shorting switch, and the discharging switch;
A power conversion device comprising:   The power converter according to claim 1 or 2, wherein a rectifier circuit that rectifies an input from an AC power supply is disposed in a first stage. A single-phase inverter having a plurality of semiconductor switch elements and a DC voltage source or an inverter circuit composed of a plurality of the single-phase inverters connected in series on the AC side;
A smoothing capacitor having one end connected via a rectifier diode to the subsequent stage of the inverter circuit;
A shorting switch having one end connected to the inverter circuit and the other end connected to the other end of the smoothing capacitor;
A series-connected switch and diode connected in parallel to a series circuit consisting of the rectifier diode and the shorting switch connected in series;
In a power converter comprising:
An inrush current prevention circuit,
A discharge switch interposed between the smoothing capacitor and the input of the inrush current prevention circuit, and connecting and separating the input of the smoothing capacitor and the inrush current prevention circuit;
A control unit for turning on and off the semiconductor switch element, the shorting switch, the switch and the discharging switch;
A power conversion device comprising:   The single-phase inverter is composed of the semiconductor switch elements connected in series and the diode or the two semiconductor switch elements connected in series, and two sets of series circuits connected in parallel, 2. The DC voltage source connected between a connection point of the semiconductor switch element and the diode in a series circuit or a connection point of the two semiconductor switch elements. 5. The power conversion device according to claim 4.   The power conversion device according to claim 1, wherein a diode is connected in reverse parallel to the shorting switch.   The power conversion device according to claim 1, further comprising a current limiting circuit. A first discharge path composed of the discharge switch, the inrush current prevention circuit, at least one semiconductor switch element, the short-circuit switch, and the smoothing capacitor;
A second discharge path including the discharge switch, the inrush current prevention circuit, at least one or more semiconductor switch elements, the DC voltage source, and the rectifier diode;
The power control device according to claim 1, wherein the control unit includes a switching unit that switches between the first discharge path and the second discharge path. Means for measuring respective voltages of the smoothing capacitor and the DC voltage source;
The switching means compares the voltage of the smoothing capacitor and the DC voltage source, and when the voltage of the smoothing capacitor is equal to or higher than the voltage of the DC voltage source, the first discharge path is effective and the second discharge path. When the voltage of the smoothing capacitor is less than the voltage of the DC voltage source, the second discharge path is enabled and the first discharge path is disabled, and the discharge path is switched to the enabled discharge path. The power converter according to claim 8, wherein   When the switching means discharges one of the discharge paths as effective, and the voltage of the smoothing capacitor or the DC voltage source included in the effective discharge path falls below a predetermined first predetermined value The power conversion device according to claim 8 or 9, wherein the discharge path that is enabled and disabled is enabled. Means for measuring the current flowing through the discharge path,
The switching means disables the effective discharge path when the current flowing through the enabled discharge path falls below a predetermined second predetermined value after discharging one of the discharge paths as effective and discharging. 9. The power conversion device according to claim 8, wherein the invalid discharge path is validated.

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