JP2686015B2 - 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 converter using a self-arc-extinguishing semiconductor element, and more particularly to a power converter with improved operating characteristics at a small current.

[0002]

2. Description of the Related Art FIG. 7 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.

The converter 3 is a U-phase switch unit SWU,
V-phase switch unit SWV, W-phase switch unit S
WW, X-phase switch unit SWX, Y-phase switch unit SWY, and Z-phase switch unit SWZ are bridge-connected.

[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 30 to 41 are diodes, and 42 to 47 are capacitors.

Here, a series circuit of a reverse blocking GTO 6 and a diode 30 connected between the DC terminal (P) and the AC terminal (U) of the converter 3 and a diode 31 and a reverse blocking G.
The U-phase switch unit SWU is connected between the DC terminal (P) and the AC terminal (V) of the converter 3 by the series circuit of TO7 and the capacitor 42 connected between the series connection points of these series circuits. Reverse blocking type GTO8 and dio-
Series circuit of the diode 32 and the diode 33 and the reverse blocking GTO
9 and a capacitor 43 connected between the series connection points of these series circuits to form the V-phase switch unit S.
WV is connected between the DC terminal (P) and the AC terminal (W) of the converter 3, and is a reverse blocking GTO 10 and diode 34.
Of the reverse blocking type GTO 11 and the series circuit of the diode 35 and the capacitor 44 connected between the series connection points of these series circuits to form the W-phase switch unit SWW.
Is a series circuit of a reverse blocking GTO 12 and a diode 36 and a series circuit of a diode 37 and a reverse blocking GTO 13 connected between the AC terminal (U) and the DC terminal (N) of the converter 3. , The X-phase switch unit SWX by the capacitor 45 connected between the series connection points of these series circuits,
A series circuit of a reverse blocking GTO 14 and a diode 38 and a series circuit of a diode 39 and a reverse blocking GTO 15 connected between the AC terminal (V) and the DC terminal (N) of the converter 3, and these. The Y-phase switch unit SWY is connected by the capacitor 46 connected between the series connection points of the series circuit of FIG. 1 and the reverse blocking GTO 16 connected between the AC terminal (W) and the DC terminal (N) of the converter 3 and the diode. -A series circuit of a diode 40 and a series circuit of a diode 41 and a reverse blocking GTO17,
The Y-phase switch unit SWY is configured by the capacitor 47 connected between the series connection points of these series circuits.

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. 7, 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 42, VCV is the voltage of the V-phase capacitor 43, V
UV is the output voltage between the U and V phases of the converter 3, and IU is the converter 3
U-phase output current, IV is V-phase output current of converter 3, VV
Is the V-phase voltage of the AC power supply 5.

FIG. 8 is a waveform diagram of each part during 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 42, VCV is the voltage of the V phase capacitor 43, and -VUV is the voltage of the converter 3. The output voltage between V phase and U phase, ICU is the current flowing into U phase capacitor 42 when diodes 30 and 31 are forward biased by the voltage of AC power supply 5, and likewise ICY.
Is Y when diodes 38 and 39 are forward biased
The current flowing into the phase capacitor 46, VGV is the voltage applied to the V-phase reverse blocking GTOs 8 and 9, and VDV is the V-phase diode.
The voltages applied to the terminals 32 and 33, VD is the DC input voltage of the converter 3, and ID is the DC input current of the converter 3.

FIG. 9 is a waveform diagram for explaining the commutation operation during the reverse conversion operation of the converter 3 of FIG.
FIG. 9 is an enlarged view of a portion “A” in FIG. 8 where commutation to a phase is performed. In FIG. 9, IU, IV, VV, VCU, VC
V, −VUV, and ICY are the same as the same symbols in FIG. The commutation operation of the converter 3 of FIG. 7 during the inverse conversion operation will be described below with reference to FIGS. 7 to 9. Before the time t1 when the commutation from the U phase to the V phase is started, the reverse blocking type GTO6,
7, 16 and 17 and the diodes 30.31, 40 and 41 are turned on, and the U-phase current IU is the reverse blocking type GTO 6 and the series circuit of the diode 30 and the diode 31 and the reverse blocking type. It flows into the GTO7 series circuit in a branched manner. Further, the W-phase current is shunted into the series circuit of the reverse blocking GTO 16 and the diode 40 and the series circuit of the diode 41 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 43 is applied in the direction of increasing IV and decreasing IU. As a result, IV flows and the current value increases, while IU decreases. The capacitor 42 is charged by the 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 t2. The capacitor 43 is continuously discharged by IV, and its voltage VCV is reached at time t3.
When becomes zero, the diodes 32 and 33 become conductive and the commutation is completed. On the other hand, during the period from time t1 to time t2, a commutation voltage represented by -VUV is generated between the V phase and the U phase, so that the voltage between the V phase and the W phase increases and becomes higher than the voltage of the capacitor 46. Therefore, the diodes 39 and 38 are forward-biased, and the current indicated by ICY flows through the capacitor 46. When the IU becomes zero and the diodes 30 and 31 are turned off at the time t2, -VUV becomes small and the voltage between the V phase and the W phase also becomes small. Therefore, ICY decreases and becomes zero at the time t4. As the ICY flows, the current value of the IV decreases by that amount. In this way, the reverse conversion operation is performed, and the DC power supplied to the converter 3 is converted into AC power and supplied to the AC power supply 5 via the AC reactor 4.

FIG. 10 is a waveform of each part when the converter 3 of FIG. 7 is performing an inverse conversion operation with a small current. In the figure, IU, IV, VV, VCU, VCV, -VUV, I
CU, ICY, VGV, VDV, and ID are the same as the same symbols in FIG. Here, the DC current ID is 1/1 of FIG.
It is set to 0. At time t5, the reverse blocking GTOs 6 and 7 are turned off, and the reverse blocking GTOs 8 and 9 are turned on.
The V-phase current IV increases and the U-phase current IU decreases to zero, and commutation from the U-phase to the V-phase is performed. Condenser 43
Is continuously discharged by IV, but since IV is small, it takes time to discharge and becomes zero at time t6. At this time, the voltage VCV of the capacitor 43 is applied in series between the DC power supply 1 and the AC power supply 5, so that the DC voltage VD becomes small as shown in the figure. When the direct current ID is further reduced, the discharge of the capacitor 43 is not completed for 60 degrees, and the direct current voltage VD is further reduced.

[0010]

As described above, in the conventional converter, when the current becomes small, it takes time to discharge the capacitor and the DC voltage becomes small. Therefore, the relationship between the DC voltage and the AC voltage is affected by the magnitude of the current, and it becomes difficult to operate especially when the current is small.

The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and the discharge time of the capacitor charge at the time of commutation is not so much influenced by the magnitude of the current so that the rated current becomes smaller than the rated current. The purpose of the present invention is to provide a power conversion device that can be operated over a wide range.

[0012]

In order to achieve this object, the present invention provides a power conversion device according to the first aspect of the present invention, which comprises a first reverse blocking self-arc-extinguishing semiconductor element and a first diode. And a second series circuit connected in parallel to the first series circuit.
A second series circuit composed of a diode and a second reverse-blocking self-extinguishing semiconductor element, and a series connection point of the first reverse-blocking self-extinguishing semiconductor element and the first diode. The second
Connected to a series connection point of the second reverse-blocking self-extinguishing semiconductor element, the first reverse-blocking self-extinguishing semiconductor element and the second reverse-blocking self The present invention is characterized in that a switch unit composed of diodes, which are respectively connected in antiparallel to arc-extinguishing semiconductor elements, is bridge-connected.

[0013]

By configuring as described above, in the power converter of FIG. 1, for example, the switch units SU and SZ
When the switch is on, turn off the switch unit SU,
In order to turn on the switch unit SV, a reverse blocking type G
When TO6 and 7 are turned off and reverse blocking type GTOs 8 and 9 are turned on, V-phase capacitor 43 → reverse blocking type GTO 9 → AC reactor 4 V phase → AC power source 5 V phase → AC power source 5 U phase → AC reactor 4, a closed loop of U phase → diode 19 → U phase capacitor 42 → diode 18 → reverse blocking GTO 8 → V phase capacitor 43 is formed. Thus V
The electric charge of the phase capacitor 43 is discharged and the U-phase capacitor 42
Therefore, even if the direct current ID becomes small, the discharge of the V-phase capacitor 43 does not prolong and the charging of the U-phase capacitor 42 does not prolong.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 1 in which the same parts as those in 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 into AC power, and 4 is an AC provided at the output of the converter 3. A reactor 5 is an AC power source or a load of the converter 3.

The converter 3 is a U-phase switch unit SU, V
Phase switch unit SV, W phase switch unit SW,
X-phase switch unit SX, Y-phase switch unit SY
, Z-phase switch unit SZ are bridge-connected.

Here, the U-phase switch unit SU is connected between the DC terminal (P) and the AC terminal (U) of the converter 3, and the series circuit and diode of the reverse blocking type GTO 6 and the diode 30. A series circuit of the reverse gate 31 and the reverse blocking GTO 7, a capacitor 42 connected between the series connection points of these series circuits, and diodes 18 and 19 connected in reverse parallel to the reverse blocking GTOs 6 and 7, respectively. Then, the V-phase switch unit SV is connected to the reverse blocking GTO 8 connected between the DC terminal (P) and the AC terminal (V) of the converter 3 and the diode.
Series circuit of the diode 32 and the diode 33 and the reverse blocking GTO
9 series circuit, a capacitor 43 connected between the series connection points of these series circuits, and diodes 20 and 21 connected in reverse parallel to the reverse blocking GTOs 8 and 9, respectively, and configured as a W-phase switch unit. SW is a reverse blocking type G connected between the DC terminal (P) and the AC terminal (W) of the converter 3.
Series circuit of TO10 and diode 34 and diode 3
5 and the reverse blocking GTO 11 in series, a capacitor 44 connected between the series connection points of these series circuits, and diodes 22 and 23 connected in reverse parallel to the reverse blocking GTOs 10 and 11, respectively. , X-phase switch unit SX
Is a series circuit of a reverse blocking GTO 12 and a diode 36 and a series circuit of a diode 37 and a reverse blocking GTO 13 connected between the AC terminal (U) and the DC terminal (N) of the converter 3. , A capacitor 45 connected between the series connection points of these series circuits, and diodes 24 and 25 connected in reverse parallel to the reverse blocking GTOs 12 and 13, respectively,
Connect the phase switch unit SY to the AC terminal (V) of the converter 3.
-Blocking GTO1 connected between the power supply and a DC terminal (N)
4 and a diode 38 in series, a diode 39 and a reverse blocking GTO 15 in series, a capacitor 46 connected between the series connection points of these series circuits, and a reverse blocking G
The Z-phase switch unit SZ is composed of diodes 26 and 27 which are connected in reverse parallel to the TOs 14 and 15, respectively, and the Z-phase switch unit SZ is connected between the AC terminal (W) and the DC terminal (N) of the converter 3 in reverse. A series circuit of the blocking GTO 16 and the diode 40, a series circuit of the diode 41 and the reverse blocking GTO 17, a capacitor 47 connected between the series connection points of these series circuits, and the reverse blocking GTOs 16 and 17 are provided. The diodes 28 and 29 are respectively connected in antiparallel.

Next, the converter 3 configured as described above.
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 42, VCV is the voltage of the V-phase capacitor 43, V
UV is the output voltage between the U and V phases of the converter 3, and IU is the converter 3
U-phase output current, IV is V-phase output current of converter 3, VV
Is the V-phase voltage of the 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 the 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 42, VCV is the voltage of the V phase capacitor 43, and -VUV is the voltage of the converter 3. Output voltage between V phase and U phase, ICU is diode 30 or 31 or diode 18 depending on the voltage of AC power supply 5.
And 19 are forward biased, the U-phase capacitor 42
The current flowing in, likewise ICY
9 or the current flowing into the Y-phase capacitor 46 when the diodes 26 and 27 are forward biased, VGV is the voltage applied to the V-phase reverse blocking type GTOs 8 and 9, and VDV is the V-phase diodes 32 and 33. The voltage, VD is the DC input voltage of the converter 3, and ID is the 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, -VUV, ICU, and ICY are the same as the same symbols in FIG. The commutation operation of the power conversion device of the present invention during reverse conversion will be described below with reference to FIGS. 1 to 3. Before the time t7 when the commutation from the U phase to the V phase is started, the reverse blocking GTOs 6, 7, 16, 17 and the diode 3 are provided.
0, 31, 40, 41 are on, and U-phase current IU
Is a series circuit of reverse blocking GTO 6 and diode 30,
It flows in a shunt into the series circuit of the diode 31 and the reverse blocking GTO 7. The W-phase current is the reverse blocking type GTO 16 and the series circuit of the diode 40, the diode 41 and the reverse blocking type GT.
It shunts into the O17 series circuit. IU and ID at this time
Are equal. At time t7, reverse blocking GTOs 6 and 7
Is turned off and the reverse blocking GTOs 8 and 9 are turned on, the voltage VCV of the capacitor 43 is added in the direction of increasing IV and decreasing IU. Thus, the IV flows and the current value increases, while the IU decreases. The capacitor 42 is charged by the IU and its voltage VCU increases. The VCU, like the VCV, increases in the IV and decreases in the IU.
Line voltage -VUV of V phase to U phase is VCV and VCU
Is the sum of After the IU becomes zero at the time t8, the diodes 19 and 18 are biased by the voltage between the U phase and the V phase of the AC power supply 5, and the charging current further flows into the capacitor 42, so that the IU flows in the negative direction. ICU is the dio at this time
It is a charging current flowing into the capacitor 42 via the terminals 19 and 18. Although the capacitor 43 is continuously discharged by the IV, the IV increases due to the inflow of ICU, and the voltage VCV of the capacitor 43 decreases faster by that amount. Time t
When VCV becomes zero at 9, diodes 32 and 33
Is conducted and the commutation is completed. ICU becomes zero at time t10. Next, at time t11, IU becomes zero. On the other hand, during the period from time t7 to t8, the voltage between the V phase and the W phase increases and becomes higher than the voltage of the capacitor 46. Therefore, the diodes 39 and 38 are forward-biased, and the current indicated by ICY flows through the capacitor 46. At time t8, when IU becomes zero and the diodes 30 and 31 are turned off, -VUV
Becomes smaller and the voltage between the V phase and the W phase also becomes smaller. Therefore, ICY decreases and becomes zero at time t12. ICY
The current value of IV is reduced by this amount due to the flow of. In this way, the reverse conversion operation is performed, and the DC power supplied to the converter 3 is converted into AC power and supplied to the AC power supply 5 via the AC reactor 4.

FIG. 4 is a waveform diagram of each part when the converter 3 of FIG. 1 is performing an inverse conversion operation with a small current. In FIG.
IU, IV, VV, VCU, VCV, -VUV, IC
U, ICY, VGV, VDV, VD and ID are the same as the same symbols in FIG. Here, the direct current ID is 1/1 of FIG.
It is set to 0.

FIG. 5 is a waveform diagram for explaining the commutation operation when the converter 3 of FIG. 1 is performing an inverse conversion operation with a small current.
FIG. 5 is an enlarged view of a portion “C” in FIG. 4 in which commutation from U phase to V phase is performed. In the figure, IU, IV, VV, VC
U, VCV, -VUV, ICU, and ICY are the same as the same symbols in FIG. Hereinafter, the commutation operation when the power conversion device according to the present invention is performing reverse conversion operation with a small current will be described with reference to FIGS. 1, 4, and 5.

Time t when the commutation from the U phase to the V phase is started
Before 13, the reverse blocking GTOs 6, 7, 16, 17 and the diodes 30, 31, 40, 41 were turned on, and the U-phase current IU was the series circuit of the reverse blocking GTO 6 and the diode 30. Then, the current flows in a shunt into the series circuit of the diode 31 and the reverse blocking GTO 7. Also, the W-phase current is the reverse blocking type GTO16.
And the diode 40 and the series circuit of the diode 41 and the reverse blocking GTO 17 are diverted. Time t31
Reverse blocking type GTO 6 and 7 are turned off at
When TO8 and 9 are turned on, the voltage VC of the capacitor 43
V is added in the direction of increasing IV and decreasing IU. As a result, IV flows and the current value increases, while IU decreases. The capacitor 42 is charged by the IU and its voltage VC
U increases. The V-phase line voltage −VUV with respect to the U-phase is the sum of VCV and VCU. After the IU becomes zero at time t14, the diodes 19 and 18 are forward-biased by the voltage between the U-phase and the V-phase of the AC power supply 5, and the capacitor 42
Since the charging current further flows in, the current flows in the negative direction. ICU
Is the charging current flowing into the capacitor 42 via the diodes 19 and 18 at this time. On the other hand, the voltage between the V phase and the W phase becomes higher than the voltage of the capacitor 46, and the diode 3
9 and 38 are forward biased, and a current indicated by ICY flows through the capacitor 46. As the ICY flows, the current value of the IV decreases by that amount. Although the capacitor 43 is continuously discharged by the IV, the IV increases due to the inflow of ICU, and the voltage VCV of the capacitor 43 decreases faster by that amount. At time t15, ICY becomes zero. When VCV becomes zero at time t16, the diodes 32 and 33 are turned on and the commutation is completed. At time t17, ICU becomes zero. At the next time t18, IU becomes zero. Thus, when the reverse blocking GTOs 6 and 7 are turned off and the reverse blocking GTOs 8 and 9 are turned on, the V-phase capacitor 43 → reverse blocking GTO 9 →
AC reactor 4 V phase → AC power source 5 V phase → AC power source 5 U phase → AC reactor 4 U phase → diode 19 →
U-phase capacitor 42 → diode 18 → reverse blocking GTO
A closed loop of the 8 → V-phase capacitor 43 is formed. Since the electric charge of the V-phase capacitor 43 is discharged and the closed loop for charging the U-phase capacitor 42 is formed in this way, the discharge of the V-phase capacitor 43 is not prolonged even if the direct current ID becomes small. Moreover, the charging of the U-phase capacitor 42 is not prolonged.

FIG. 6 is a block diagram showing another embodiment of the present invention. In the figure, 1 to 5 and 30 to 47 are the same as the same symbols in FIG. Reference numerals 48 to 59 are reverse conducting self-extinguishing elements, for example, reverse conducting GTOs. Reverse conduction type GTO
Is functionally the same as the anti-parallel GTO and diode anti-parallel circuit described in FIG. Therefore, the power conversion operation is the same as that described with reference to FIGS.

[0025]

As described above, the power converter according to the present invention does not prolong the charging / discharging time of the capacitor of the switch unit even when operating with a small current, and the Almost no change in voltage occurs. Therefore, by adopting the present invention, it is possible to provide a power conversion device capable of stable operation over a wide current range from the rated current to the minute current.

[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 waveform diagram of each part in the inverse conversion operation at the time of a small current of the power conversion device of the present invention.

FIG. 5 is a waveform diagram for explaining the commutation operation of the power conversion device of the present invention during the reverse small current conversion operation.

FIG. 6 is a configuration diagram showing another embodiment of the power conversion device of the invention.

FIG. 7 is a configuration diagram of a conventional power conversion device.

FIG. 8 is a waveform diagram of each part during the inverse conversion operation of the conventional power conversion device.

FIG. 9 is a waveform diagram for explaining a commutation operation during a reverse conversion operation of the conventional power conversion device.

FIG. 10 is a waveform diagram of each part when the conventional power conversion device is performing reverse conversion operation with a small current.

[Explanation of symbols]

 1 ...... DC power supply 2 ...... DC reactor 3 ...... Converter 4 ...... AC reactor 5 ...... AC power supply 6-17 ...... Reverse blocking type GTO 18-41 ...... Diode 42-47 ...... Capacitor 48- 59 ...... Reverse conduction type GTO

Claims (2)

(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 reverse-blocking self-extinguishing semiconductor device, wherein a power conversion device is configured by bridge-connecting a switch unit composed of a capacitor connected to a series connection point of the first reverse-blocking self-extinguishing device constituting the switch unit. An electric power conversion device characterized in that diodes are respectively connected in antiparallel to the arc-extinguishing semiconductor element and the second reverse blocking self-extinguishing semiconductor element. 2. A first series circuit composed of a first reverse conducting self-extinguishing semiconductor device and a first diode, and a second diode connected in parallel to the first series circuit. Second
Second series circuit composed of the reverse conduction type self-arc-extinguishing semiconductor element, the series connection point of the first reverse conduction type self-extinguishing semiconductor element and the first diode, and the second diode. And the second
Of the reverse conduction type self-extinguishing semiconductor device and the power conversion device configured by bridge-connecting a switch unit composed of a capacitor connected to the series connection point.