JP2712095B2 - Power converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power conversion device using a self-extinguishing semiconductor device, and more particularly to a power conversion device in which the voltage applied to the self-extinguishing semiconductor device is reduced.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing an embodiment of a conventional power converter. In the figure, 1 is a DC power supply, 2 is a DC reactor for smoothing the output of the DC power supply 1, 3 is a converter for converting DC power to AC power, 4 is an AC reactor provided at the output of the converter 3, and 5 is It is an AC power supply or a load of the converter 3.

[0003] Each phase arm constituting the converter 3 has a U-phase switch unit SWU, a V-phase switch unit SWV, W
Phase switch unit SWW, X-phase switch unit SW
It is composed of an X and Y phase switch unit SWY and a Z phase switch unit SWZ.

[0004] Reference numerals 6 to 17 denote reverse blocking self-extinguishing semiconductor elements constituting the converter 3, for example, a reverse blocking gate transistor.
Thyristor (hereinafter referred to as reverse blocking GTO)
Reference numerals 18 to 29 denote diodes, and reference numerals 30 to 35 denote capacitors.

Here, a series circuit of a reverse blocking GTO 6 and a diode 18 connected between a DC terminal (P) and an AC terminal (U) of the converter 3, and a diode 19 and a reverse blocking G
A U-phase switch unit SWU, which forms a U-phase arm by a series circuit of TO7 and a capacitor 30 connected between series connection points of these series circuits, is connected to a DC terminal (P) and an AC terminal ( V) and the reverse blocking type G
Series circuit of TO8 and diode 20 and diode 21
And a series circuit of the reverse blocking type GTO 9 and a V-phase switch unit SWV constituting a V-phase arm by a capacitor 31 connected between the series connection points of these series circuits. Between the series circuit of the reverse blocking GTO 10 and the diode 22 and the series circuit of the diode 23 and the reverse blocking GTO 11 connected between the power supply and the AC terminal (W), and between the series connection points of these series circuits. The W-phase switch unit SWW, which forms a W-phase arm by the connected capacitor 32, is connected to an AC terminal (U) and a DC terminal (N) of the converter 3.
Reverse blocking GTO12 and diode 2 connected between
4 series circuit and diode 25 and reverse blocking GTO13
And a capacitor 33 connected between the series connection points of these series circuits and an X-phase switch unit SWX forming an X-phase arm.
-Blocking GTO1 connected between the power supply and a DC terminal (N)
4 and a series circuit of a diode 26 and a series circuit of a diode 27 and a reverse blocking GTO 15 and a capacitor 34 connected between series connection points of these series circuits.
The Y-phase switch unit SWY constituting the system is connected to the converter 3
Series circuit of reverse blocking GTO 16 and diode 28 and series circuit of diode 29 and reverse blocking GTO 17 connected between AC terminal (W) and DC terminal (N), and series circuit of these. 3 connected between series connection points of
5, a Y-phase switch unit S constituting a Y-phase arm
Configure WY.

Next, the converter 3 constructed as described above is used.
The operation of converting the power of the DC power supply 1 to AC and supplying the AC power to the AC power supply 5, that is, the so-called reverse conversion, will be described. In FIG. 4, VD is the DC input voltage of the converter 3,
ID is the DC input current of the converter 3, VCU is the voltage of the U-phase capacitor 30, VCV is the voltage of the V-phase capacitor 31,
UV is the line voltage between the U-phase and V-phase of the converter 3, IU is the U-phase output current of the converter 3, IV is the V-phase output current of the converter 3, and VV is the V-phase voltage of the AC power supply 5. is there.

FIG. 5 is a waveform diagram of each part at the time of the inverse conversion operation of the converter 3 of FIG. In the figure, IU is U of converter 3
Phase output current, IV is the V-phase output current of the converter 3, VV is the V-phase voltage of the AC power supply 5, VCU is the voltage of the U-phase capacitor 30, VCV is the voltage of the V-phase capacitor 31, and -VUV is the voltage of the converter 3. Line voltage between V-phase and U-phase, ICU is AC power supply 5
The current flowing into the U-phase capacitor 30 when the diodes 19 and 18 are forward-biased by the
CY is a current flowing into the Y-phase capacitor 34 when the diodes 27 and 26 are forward biased, VGU is a voltage applied to the U-phase reverse blocking GTOs 6 and 7, and VDU is applied to the U-phase diodes 18 and 19. Voltage and VD are the DC input voltage of the converter 3 and ID is the DC input current of the converter 3.

FIG. 6 is a waveform diagram for explaining a commutation operation at the time of the inverse conversion operation of converter 3 in FIG.
It is an enlarged view of the part of "A" of FIG. 5 in which commutation to a phase is performed. In FIG. 6, IU, IV, VV, VCU, VC
V, -VUV, ICU and ICY are the same as the same symbols in FIG. The commutation operation during the reverse conversion operation of the converter 3 of FIG. 4 will be described below with reference to FIGS. Before time t1 when commutation from the U-phase to the V-phase starts, the reverse blocking GT
O6, 7, 16, 17 and diodes 18.19, 28,
29 is on, and the U-phase current IU is the reverse blocking GTO
6 and a series circuit of a diode 18 and a series circuit of a diode 19 and a reverse blocking GTO 7. Further, the W-phase current is divided and flows to a series circuit of the Z-phase reverse blocking GTO 16 and the diode 28 and a series circuit of the diode 29 and the reverse blocking GTO 17. At this time, IU and ID are equal. At time t1, when the reverse blocking GTOs 6 and 7 are turned off and the reverse blocking GTOs 8 and 9 are turned on, the voltage VCV of the capacitor 31 increases in the direction of increasing IV and decreasing IU. As a result, IV flows and the current value increases, while IU decreases. Capacitor 30 is charged by IU and its voltage VCU increases. VCU is also I like VCV.
Participants increase V and decrease IU. At this time, the V-phase line voltage -VUV with respect to the U-phase is VCV and VCU.
Is the sum of IU goes to zero at time t2. Capacitor 31 is continuously discharged by the IV, and when its voltage VCV becomes zero at time t3, diodes 20 and 21 are discharged.
Is conducted, and the IV is divided and flows into the series circuit of the reverse blocking GTO 8 and the diode 20 and the series circuit of the diode 21 and the reverse blocking GTO 9 to complete the commutation. On the other hand, during the period from time t1 to t2, -VU
A commutation voltage indicated by V is generated, so that the voltage between the V phase and the W phase increases and becomes higher than the voltage of the capacitor 34. Accordingly, the diodes 27 and 26 are forward-biased, and a current indicated by ICY flows through the capacitor 34. At time t2, IU goes to zero and diodes 18 and 19 turn off.
-VUV decreases and the voltage between the V and W phases also decreases, so that ICY decreases to zero at time t4. As the ICY flows, the current value of the IV decreases by that amount. Next, at time t5, -VUV changes to VCU.
When it becomes larger, the diodes 19 and 18 become forward biased, and the current indicated by ICU flows through the capacitor 30, and VC
U increases with increasing -VUV. ICU is at time t
It once becomes zero at 6, but flows again during the period from time t7 to t8. Next, at time t9 when 60 electrical degrees have elapsed from time t1, commutation from the Z phase to the X phase is performed.
At this time, a commutation voltage is generated between the W phase and the U phase, so that the voltage between the V phase and the U phase increases, and the diodes 19 and 1
8 is forward biased and the charging current ICU flows through the capacitor 30.

This is exactly the same phenomenon as charging current ICY flowing through capacitor 34 during the period from time t1 to time t4. At time t10, the ICU becomes zero. At this time, the VCU is charged to a voltage higher than the peak value of -VUV. The voltage VCU of the capacitor 30 is a reverse blocking GTO6
And 7 in the forward direction, so that the reverse blocking GTOs 6 and 7
Is applied with a voltage as shown by VGU in FIG. Here, the maximum value of VGU occurs when diodes 19 and 18 are forward biased and conducting, and is equal to the maximum value of VCU.

[0010]

As described above, in the conventional power converter, the U-phase, V-phase and W-phase
The commutation voltage generated during the commutation of the phase arm, that is, the positive arm, is applied to the X-phase, Y-phase, and Z-phase arms, that is, the negative arm,
The capacitor of the negative arm is charged and the voltage applied to the reverse blocking GTO of the negative arm increases. Similarly, the commutation voltage generated at the time of commutation of the negative arm is applied to the positive arm, the capacitor of the positive arm is charged, and the reverse blocking type G of the positive arm is applied.
The voltage applied to TO increases. Therefore, when a reverse blocking GTO having a predetermined forward voltage tolerance is used, the circuit voltage must be reduced and used by an amount corresponding to an increase in the voltage, so that the output of the power converter must be reduced.

The present invention has been made to eliminate the above-mentioned drawbacks of the prior art, and is intended to prevent the commutation voltage of the positive arm from being applied to the negative arm and to reduce the negative arm. It is an object of the present invention to provide a power converter that can use the power converter at a higher circuit voltage by preventing the commutation voltage of the power converter from being applied to the positive arm.

[0012]

According to the present invention, there is provided a first reverse blocking self-extinguishing semiconductor device comprising:
A first series circuit comprising a diode and a second series circuit comprising a second diode connected in parallel with the first series circuit and a second reverse blocking self-extinguishing semiconductor device. A first reverse blocking self-extinguishing semiconductor device and a first diode;
And a switch unit comprising a capacitor connected between a series connection point of the second diode and a series connection point of the second diode and the second reverse blocking type self-extinguishing semiconductor device, and a series connection to the switch unit. Each phase arm of the power converter is constituted by a reactor to be used.

[0013]

As described above, by connecting the reactors to the positive side switch unit and the negative side switch unit, mutual interference during commutation of the positive side arm and the negative side arm is eliminated, and the reverse blocking type is provided. The voltage applied to the self-extinguishing semiconductor element can be reduced.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, 1 is a DC power supply, 2 is a DC reactor for smoothing the output of the DC power supply 1, 3 is a converter for converting DC power to AC power, 5 is an AC power supply or a load of the converter 3. is there. Here, the U-phase switch unit S
A series circuit of U and reactor 36 is connected between a DC terminal (P) and an AC terminal (U) to form a U-phase arm of converter 3, and a V-phase switch unit SV and reactor 37 are connected in series. The circuit is connected between a DC terminal (P) and an AC terminal (V) to form a V-phase arm of the converter 3, and a series circuit of the W-phase switch unit SW and the reactor 38 is connected to a DC terminal ( P) and the AC terminal (W) to connect
A phase arm is formed, and a series circuit of the reactor 39 and the X-phase switch unit SX is composed of an AC terminal (U) and a DC terminal (N).
To form an X-phase arm.
And a series circuit of the Y-phase switch unit SY are connected between an AC terminal (V) and a DC terminal (N) to form a Y-phase arm, and a series circuit of the reactor 41 and the Z-phase switch unit SZ is connected to the AC terminal. A Z-phase arm is formed by connecting between the terminal (W) and the DC terminal (N).

A U-phase switch unit SU is connected to a series circuit of a reverse blocking GTO 6 and a diode 18 and a diode 19 and a reverse blocking GTO connected in parallel to this series circuit.
7 and a capacitor 30 connected between the series connection points of these series circuits. A V-phase switch unit Sv is connected in parallel with the series circuit of the reverse blocking GTO 8 and the diode 20 and the series circuit. Diode 21 to be connected
And a series circuit of the reverse blocking GTO 9 and a capacitor 31 connected between the series connection points of these series circuits,
The W-phase switch unit SW is connected to a series circuit of a reverse blocking GTO10 diode 22, a series circuit of a diode 23 and a reverse blocking GTO11 connected in parallel to this series circuit, and a series connection point of these series circuits. The X-phase switch unit SX is constituted by a capacitor 32 connected therebetween, and a series circuit of a reverse blocking GTO 12 diode 24 and a diode 25 and a reverse blocking G connected in parallel to this series circuit.
It comprises a series circuit of TO13 and a capacitor 33 connected between the series connection points of these series circuits. The Y-phase switch unit SY is connected in parallel with the series circuit of the reverse blocking GTO14 diode 26 and this series circuit. Dio
And a capacitor 34 connected between the series connection points of these series circuits, and the Z-phase switch unit SZ is connected to the reverse blocking GTO 15.
It comprises a series circuit of six diodes 28, a series circuit of a diode 29 and a reverse blocking GTO 17 connected in parallel with this series circuit, and a capacitor 35 connected between the series connection points of these series circuits. .

Next, the converter 3 configured as described above is used.
The operation of converting the power of the DC power supply 1 to AC and supplying the AC power to the AC power supply 5, that is, the so-called reverse conversion, will be described. In FIG. 1, VD is the DC input voltage of the converter 3,
ID is the DC input current of the converter 3, VCU is the voltage of the U-phase capacitor 30, VCV is the voltage of the V-phase capacitor 31,
UV is the line between the junction of the U-phase arm reverse blocking GTO 7 cathode and reactor 36 of the converter 3 and the V-phase arm reverse blocking GTO 9 cathode and reactor 37 connection point. Voltage, IU is the U-phase output current of converter 3, IV is the V-phase output current of converter 3, and VV is the V-phase voltage of AC power supply 5.

FIG. 2 is a waveform diagram of each part during the inverse conversion operation of the converter 3 of FIG. In FIG. 2, IU is the U of converter 3.
Phase output current, IV is the V-phase output current of the converter 3, VV is the V-phase voltage of the AC power supply 5, VCU is the voltage of the U-phase capacitor 30, VCV is the voltage of the V-phase capacitor 31, and -VUV is the voltage of the converter 3. Connection point between cathode of V-phase arm reverse blocking GTO 9 and reactor 37 and reverse blocking GTO 7 of U-phase arm
Line voltage at the connection point between the cathode and the reactor 36, IC
U is a current flowing into the U-phase capacitor 30 when the diodes 19 and 18 are forward-biased by the voltage of the AC power supply 5, and ICY is a Y-phase capacitor when the diodes 27 and 26 are forward-biased. Current flowing into 34,
VGU is the voltage applied to the U-phase reverse blocking GTOs 6 and 7;
DU is the voltage applied to U-phase diodes 18 and 19, VD
Is a DC input voltage of the converter 3, and ID is a DC input current of the converter 3.

FIG. 3 is a waveform diagram for explaining the commutation operation of the converter 3 of FIG. 1, and is an enlarged view of the "B" portion of FIG. 2 in which commutation from the U phase to the V phase is performed. In the figure, IU, I
V, VV, VCU, VCV, -VUV, ICU, ICY
Is the same as the same symbol in FIG.

Hereinafter, a commutation operation at the time of reverse conversion of the power converter of the present invention will be described with reference to FIGS. From U phase to V
Before time t11 when commutation to the phase starts, the reverse blocking G
TO6,7,16,17 and diodes 18,19,2
8, 29 are on, and the U-phase current IU
Series circuit of TO6 and diode 18 and diode 19
And flows into the series circuit of the reverse blocking type GTO7. Further, the W-phase current is divided and flows through a series circuit of the reverse blocking GTO 16 and the diode 28 and a series circuit of the diode 29 and the reverse blocking GTO 17. At this time, IU and ID are equal. At time t11, when the reverse blocking GTOs 6 and 7 are turned off and the reverse blocking GTOs 8 and 9 are turned on, the voltage VCV of the capacitor 31 increases in the direction of increasing the V-phase current IV and decreasing IU. Thus, the IV flows and the current value increases, while the IU decreases. Capacitor 30 is charged by IU and its voltage VCU increases. The VCU, like the VCV, increases in the IV and decreases in the IU. The V-phase line voltage −VUV with respect to the U-phase is the sum of VCV and VCU. IU becomes zero at time t12. Capacitor 3
1 is continuously discharged by the IV. When the voltage VCV becomes zero at time t13, the diodes 20 and 21 become conductive, and the IV becomes a series circuit of the reverse blocking GTO 8 and the diode 20, and the diode 21 and the diode 21. A state where the current is diverted into the series circuit of the reverse blocking GTO 9 and the flow is completed is completed. Next, at time t14, when -VUV becomes larger than VCU, diodes 19 and 18 are forward-biased and capacitor 30 is turned on.
, A current indicated by ICU flows, and VCU increases with an increase in -VUV. The ICU temporarily goes to zero at time t15, but flows again during the period from time t16 to t18. Next, at time t17 when 60 electrical degrees have elapsed from time t11, Z
The commutation from the phase to the X phase is performed. The negative arm and the positive arm are connected to the reactors 41 and 39 and the reactors 36 and 37.
, The commutation voltage of the negative arm does not appear at -VUV. The ICU flows again from time t19 and becomes zero at time t20 to complete charging. At this time, VCU
Is charged to a value equal to the peak value of -VCV. The voltage VCU of the capacitor 30 is applied to the reverse blocking GTOs 6 and 7 in the forward direction, so that the reverse blocking GTOs 6 and 7 have VG of FIG.
A voltage as shown by U is applied. Where VG
The maximum value of U is equal to the maximum value of VCU. In the above description, the reverse blocking type GTO is used as an example of the switching element, but the same effect can be obtained by using another self-extinguishing element.

Also, the arc constituting the power conversion device of the present invention.
The system is not limited to the embodiment of FIG. 1, but can be implemented similarly even if the connection relation between the switch unit and the reactor is reversed. That is, the reactor is not limited to being connected between the AC terminal and the switch unit, but can be similarly implemented by connecting between the DC terminal and the switch unit.

[0022]

As described above, the power conversion device according to the present invention separates the positive arm and the negative arm by the reactor, so that the commutation voltage of the positive arm is reduced. Of the negative arm and the effect of the commutation voltage of the negative arm on the positive arm. Therefore,
As described above, the voltage applied to the reverse blocking GTO can be kept low. In contrast to the maximum value of VGU in the operation example of the conventional power converter described in FIG. 5, the operation example of the power converter of the present invention in FIG. 2 operates under the condition that the voltage of the AC power supply 5 and the current of each section are equal. And the maximum value of VGU is 72% of FIG.
Met. The maximum value of VGU is limited by the voltage rating of the reverse blocking GTO used,
If the maximum value of VGU is made equal using
The power converter of the present invention can reduce the voltage of the AC power supply 5 to 139%. Therefore, 39 times more than the conventional power converter.
By obtaining an extra% output, the economic effect is great.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a power conversion device of the present invention.

FIG. 2 is a waveform diagram of each part during the reverse conversion operation of the power conversion device of the present invention.

FIG. 3 is a waveform diagram of each part in a commutation operation at the time of the reverse conversion operation of the power converter of the present invention.

FIG. 4 is a configuration diagram of a conventional power converter.

FIG. 5 is a waveform diagram of each unit during a reverse conversion operation of the conventional power converter.

FIG. 6 is a waveform diagram for explaining a commutation operation at the time of a reverse conversion operation of the conventional power converter.

[Explanation of symbols]

 1 DC power supply 2 DC reactor 3 Converter 4 AC reactor 5 AC power supply 6-17 Reverse blocking GTO 18-29 Diode 30-35 Capacitor 36- 41 ...... Reactor

Claims (1)

(57) [Claims] 1. A first series circuit comprising a first reverse blocking type self-extinguishing semiconductor device and a first diode, and a second diode connected in parallel to the first series circuit. Second
A second series circuit comprising a reverse blocking type self-extinguishing semiconductor device, a series connection point of the first reverse blocking type self-extinguishing semiconductor device and a first diode, and a second diode. And the second
A switch unit consisting of a capacitor connected between the reverse blocking type self-extinguishing semiconductor element and a series connection point of the above, and a reactor connected in series with the switch unit to constitute each phase arm of the power converter. A power converter characterized by the above-mentioned.