JP2718857B2 - 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 reverse conducting self-extinguishing semiconductor device, and more particularly to a power converter having improved characteristics in an operation region for supplying a leading current to a power supply.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram showing an example of such a conventional power converter. In the figure, 1 is a DC power supply, 2 is a DC reactor, 3 is a converter, 4 is an AC reactor, 5
Is an AC power supply. Reference numerals 7 to 18 denote reverse conducting self-turn-off quenching thyristors (hereinafter referred to as reverse conducting GTOs), which constitute the converter 3.
) Will be described. 19
Reference numerals 30 to 30 denote diodes, and reference numerals 31 to 36 denote capacitors.
Here, the U-phase switch unit is formed by the GTOs 7, 8 and the diodes 19, 20 and the capacitor 31, and the GTOs 9, 1
0, diodes 21 and 22 and a capacitor 32 to form a V-phase switch unit.
The G-phase switch unit is constituted by the GTOs 3 and 24 and the capacitor 33, the X-phase switch unit is constituted by the GTOs 13 and 14, the diodes 25 and 26 and the capacitor 34, and the GTO 1
The Y-phase switch unit is constituted by 5, 16, the diodes 27, 28 and the capacitor 35, and the Z-phase switch unit is constituted by the GTOs 17, 18, the diodes 29, 30 and the capacitor 36.

The operation of the above configuration for supplying a leading current to the AC power supply 5 will be described. In the figure,
(P) and (N) are DC terminals of the converter 3, (U) and (V)
(W) is the AC terminal of the converter 3, VD is the DC voltage of the converter 3, ID is the DC power supply of the converter 3, VCU is the voltage of the U-phase capacitor 31, VCV is the voltage of the V-phase capacitor 32, V
UV is the U-phase V-phase line voltage of the power supply 5, and IU is the U-phase voltage of the converter 3.
The phase output current, IV, is the V-phase output current of converter 3 and VU is the U-phase voltage of AC power supply 5.

FIG. 8 is a waveform diagram showing the operation when the conventional power converter of FIG. 7 supplies a leading current to the AC power supply 5 at a control delay angle of 90 °. In FIG. 8A, the IU
Is the U-phase output current of converter 3, and IV is the V
VU is a U-phase voltage of the AC power supply 5. In FIG. 8B, VCU is the voltage of the U-phase capacitor 31, VCV is the voltage of the V-phase capacitor 32, and VUV is the U-phase V-phase line voltage of the power supply 5. FIG.
In (c), ICU is a charging current flowing into the U-phase capacitor 31 when the reverse conducting GTOs 7 and 8 are conducting in the reverse direction, and ID is a DC current of the converter 3. FIG. 8 (d)
Where VD is the DC voltage of converter 3 and VGU is U
VD is the voltage applied to the reverse conducting GTOs 7 and 8,
U is a voltage applied to the U-phase diodes 19 and 20.

Hereinafter, a commutation operation of the conventional power converter will be described with reference to FIG. 7 and FIG. Before time t1 when commutation from the U-phase to the V-phase starts, the reverse conducting GTO 7,
8, 17, 18 and the diodes 19, 20, 29, and 30 are on, and the U-phase current IU is divided into a series circuit of the reverse conducting GTO 7 and the diode 19 and a series circuit of the diode 20 and the reverse conducting GTO 8. Flow and flow. The W-phase current is divided and flows into a series circuit of the reverse conducting GTO 17 and the diode 29 and a series circuit of the diode 30 and the reverse conducting GTO 18. At this time, IU and ID are equal. At time t1, reverse conduction type GTOs 7 and 8 are turned off, and reverse conduction type GTOs 7 and 8 are turned off.
When O9 and O9 are turned on, the voltage V
CV joins increasing IV and decreasing IU. As a result, IV flows and the current value increases, while IU decreases. Capacitor 31 is charged by IU and its voltage VCU increases. The VCU, like the VCV, increases in the IV and decreases in the IU. IU becomes zero at time t2, and reverse conducting GTOs 7 and 8 are turned off.

However, at this time, the sum of the voltage VUV between the U-phase and V-phase lines of the AC power supply 5 and the voltage VCV of the capacitor 32 is applied in the opposite direction to the reverse conducting GTOs 7 and 8,
The reverse conducting GTOs 7 and 8 are energized in the reverse direction, and the charging current ICU flows into the capacitor 31. Therefore, voltage VCU of capacitor 31 increases. IC at time t3
U becomes zero, and the charging of the capacitor 31 is completed.

As described above, the capacitor 31 is charged by the sum of the U-phase V-phase line voltage VUV of the AC power supply 5 and the voltage VCV of the capacitor 32, and the charge is gradually accumulated to increase the voltage VCU. I will do it. Therefore, voltage VGU applied to U-phase reverse conducting GTOs 7 and 8 and voltage VDU applied to U-phase diodes 19 and 20 gradually increase and become excessive. The same applies to other phases.

[0008]

As described above, in the conventional converter, the voltage of the capacitors 31 to 36 gradually increases in the operation region in which the power is supplied to the power supply 5 and the current is supplied, and the reverse conducting GTOs 7 to 18 and Since there is a phenomenon that the voltage applied to the diodes 19 to 30 becomes excessive, operation in this region cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made to eliminate the above-mentioned drawbacks of the conventional conversion device, and suppresses an increase in the voltage of a capacitor so as to operate even in an operation region in which a current is supplied to a power supply. It is intended to provide a device.

[0010]

According to a first aspect of the present invention, a cathode of a first reverse conducting self-extinguishing semiconductor device and an anode of a first diode are connected. One common connection point, the cathode of the second diode and the anode of the second reverse conducting self-extinguishing semiconductor device are connected to form a second common connection point, and one end of a capacitor is connected to the first common connection point. And the other end of the capacitor is connected to the second common connection point, and the anode of the first reverse conducting self-extinguishing semiconductor device and the anode of the second diode are connected in common. As a common connection point for
The cathode of the first diode and the cathode of the second reverse conducting self-extinguishing semiconductor element are commonly connected to form a fourth common connection point, and the third common connection point and the fourth common connection In a power converter including a switch unit having a point as a terminal as a minimum component,

[0011] The power conversion apparatus according to the present invention, further comprising voltage suppression means for bypassing a current flowing into the capacitor when the voltage of the capacitor exceeds a predetermined value, and suppressing a rise in the voltage of the capacitor. is there.

[0012]

According to the first aspect of the present invention, the power converter is provided even in an operation region in which the power is supplied to the power supply by providing voltage suppressing means for suppressing the voltage of the capacitor from exceeding a predetermined value. Can drive.

[0013]

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a DC power supply, 2 is a DC reactor,
Reference numeral 3 denotes a converter, 4 denotes an AC reactor, 5 denotes an AC power supply, and 6 denotes a voltage suppression circuit. 7 to 18 are reverse conducting GTOs constituting the converter 3, 19 to 30 are diodes, and 31 to 36 are capacitors. Here, a U-phase switch unit is constituted by the GTOs 7, 8 and the diodes 19, 20 and the capacitor 31, a V-phase switch unit is constituted by the GTOs 9, 10 and the diodes 21, 22 and the capacitor 32, and the GTO 11,
12, a diode 23, 24 and a capacitor 33 constitute a W-phase switch unit, GTOs 13, 14 and diodes 25, 26 and a capacitor 34 constitute an X-phase switch unit, and GTOs 15, 16 and diodes 27, 28 and a capacitor 35 constitute a Y-phase switch unit. To GTO1
The Z-phase switch unit is constituted by the elements 7, 18, the diodes 29, 30 and the capacitor 36.

The configuration described above is the same as that of the conventional power converter shown in FIG. 7, except that a voltage suppressing means, for example, a voltage suppressing circuit described below is provided. The voltage suppression circuit is 37-4
2 is a diode, 43 is a capacitor, and 44 is an energy absorption circuit.

FIG. 2 is a detailed diagram of a voltage suppression circuit according to one embodiment of the present invention. In the figure, reference numerals 37 to 44 are the same as the same symbols in FIG. 45 is an AC power supply for the converter 3, 46 is another AC power supply for regenerating the absorbed energy, and 47 to 52 are thyristors. The operation in the case of supplying the leading current to the AC power supply 5 in the above configuration will be described. In the figure, P and N are DC terminals of the converter 3, U, V and W are AC terminals of the converter 3, VD is a DC voltage of the converter 3, ID is a DC power supply of the converter 3, and VCU is U The voltage of the phase capacitor 31,
VCV is the voltage of the V-phase capacitor 32, VUV is the U-phase V-phase line voltage of the power supply 5, IU is the U-phase output current of the converter 3, I
V is a V-phase output current of the converter 3 and VU is a U-phase voltage of the AC power supply 5.

FIG. 6 is a waveform chart showing the operation when the power converter of the present invention supplies a leading current to the AC power supply 5 at a control delay angle of 90 °. In FIG. 6A, IU is the U-phase output current of the converter 3, IV is the V-phase output current of the converter 3, and VU is the U-phase voltage of the AC power supply 5. In FIG. 6B, VCU is the voltage of the U-phase capacitor 31, VCV is the voltage of the V-phase capacitor 32,
VUV is the U-phase V-phase line voltage of the power supply 5. Further FIG.
In (c), ICU is a charging current flowing into the U-phase capacitor 31 through reverse conduction of the GTOs 7 and 8 in the reverse direction, and ICLU is a charging current flowing into the capacitor 43 via the diodes 37 and 41. And ID is the DC current of the converter 3. In FIG. 6D, VD is a DC voltage of the converter 3, and VGU is a U-phase reverse conducting GTO7.
VDU is the voltage across U-phase diodes 19 and 20.

Hereinafter, the commutation operation of one embodiment of the power converter of the present invention will be described with reference to FIGS. 1, 2 and 6.
Before time t4 when commutation from the U phase to the V phase is started,
Reverse conducting GTO 7, 8, 17, 18 and diode 19,
20, 29, and 30 are turned on, and the U-phase current IU shunts and flows through the series circuit of the reverse conducting GTO 7 and the diode 19 and the series circuit of the diode 20 and the reverse conducting GTO 8. The W-phase current is supplied to a series circuit of the reverse conducting GTO 17 and the diode 29, and the diode 30 and the reverse conducting GTO 18
And flows into the series circuit of

At this time, IU and ID are equal. At time t4, reverse conduction type GTOs 7 and 8 are turned off, and reverse conduction type GTOs 7 and 8 are turned off.
When O9 and O9 are turned on, the voltage V
CV increases in IV and decreases IU.
Thus, the IV flows and the current value increases, while the IU decreases. The capacitor 31 is charged by the IU and its voltage V
CU increases. Like the VCV, the VCU also increases the IV and decreases the IU. IU is at time t
It becomes zero at 5 and the reverse conducting GTOs 7 and 8 are turned off.

However, at this time, the voltage of the sum of the U-phase V-phase line voltage VUV of the AC power supply 5 and the voltage VCV of the capacitor 32 is applied to the reverse conduction type GTOs 7 and 8 in the opposite direction.
The reverse conducting GTOs 7 and 8 are energized in the reverse direction, and the charging current ICU flows into the capacitor 31. Therefore, voltage VCU of capacitor 31 increases. At time t6, when voltage VCU of capacitor 31 becomes larger than the voltage of capacitor 43, diodes 37 and 41 conduct, and current flows into current ICU capacitor 43 flowing into capacitor 31 via reverse conducting GTOs 8 and 7. I do. At this time, the current flowing into the capacitor 43 is ICLU. Assuming that the capacitance of the capacitor 43 is sufficiently larger than the capacitance of the capacitor 31, the current ICU flowing into the capacitor 31 via the reverse conducting GTOs 8 and 7 becomes substantially zero, and the voltage of the capacitor 31 rises. Is suppressed. At time t7, ICLU becomes zero, and charging of the capacitor 43 is completed. The same applies to the commutation operation in other phases,
At the time of commutation from the Z phase to the X phase, the ICLZ flows and suppresses a rise in the voltage of the capacitor 36. At the time of commutation from the V phase to the W phase, ICLV flows and suppresses a rise in the voltage of the capacitor 32. At the time of commutation from the X-phase to the Y-phase, ICLX flows and suppresses a rise in the voltage of the capacitor 34. At the time of commutation from the W phase to the U phase, the ICLW flows and suppresses a rise in the voltage of the capacitor 33. At the time of commutation from the Y phase to the Z phase, ICLY flows and suppresses a rise in the voltage of the capacitor 35. The capacitors 43 include ICLU to ICLW and ICLX to ICL
Since Z flows in and charges are accumulated, it is necessary to absorb this energy. Reference numeral 44 denotes an example of an energy absorption circuit, which is regenerated to another AC power supply 46 by an inverse conversion circuit composed of thyristors 47 to 52.

FIG. 3 is a diagram showing a voltage suppression circuit according to a second embodiment of the power converter of the present invention. In the figure, 37-4
5 is the same as the same symbol in FIG. 53 is GTO, 54
Is a resistor. The GTO 53 and the resistor 54 constitute the energy absorbing circuit 44. The voltage can be suppressed by turning on / off the GTO 53 so that the voltage of the capacitor 43 does not exceed a predetermined value and consuming the electric charge accumulated in the capacitor 43 by the resistor 54.

FIG. 4 is a diagram showing a voltage suppressing circuit according to a third embodiment of the power converter of the present invention. In the figure, 37-4
Reference numerals 2 and 45 are the same as those in FIG. Reference numeral 55 denotes a non-linear resistance element having a characteristic that when a voltage higher than a predetermined voltage is applied, the resistance value sharply decreases. When the voltage of the AC power supply 45 of the converter 3 exceeds a predetermined value, the resistance value of the non-linear resistance element 55 decreases rapidly, and the voltage can be suppressed.

FIG. 5 is a diagram showing a voltage suppressing circuit according to a fourth embodiment of the power converter of the present invention. In the figure, 45 is the same as the same symbol in FIG. Reference numerals 56 to 58 denote non-linear resistance elements having a characteristic that when a voltage higher than a predetermined voltage is applied, the resistance value sharply decreases. When the voltage of the AC power supply 45 of the converter 3 exceeds a predetermined value, the nonlinear resistance elements 56 to
The resistance value of 58 is rapidly lowered, and the voltage can be suppressed.

As described above, according to the embodiment of the present invention, the phenomenon in which the voltage of the capacitors 31 to 36 increases can be suppressed, so that the operation in the region in which the current is supplied to the AC power supply 5 is supplied. Becomes possible. Also, comparing the operation waveform of the conventional converter of FIG. 8 with the operation waveform of the converter of the embodiment of the present invention of FIG. 6, the maximum value of the voltage VCU of the capacitor 31 is as follows. Of 52%. Also, the maximum value of the voltage VGU applied to the GTOs 7 and 8 was 59% for the converter of the present invention compared to the conventional converter. Further, the voltage VD applied to the diodes 19 and 20
The maximum value of U is that the converter of the present invention is 52% of the conventional converter.
Met. The current ICLU flowing into the capacitor 43
-ICLW and ICLX-ICLZ averaged 1.4% of DC current ID. Therefore, the voltage applied to the converter can be greatly reduced by the small-capacity voltage suppression circuit 6, and the economic effect is large.

[0024]

According to the present invention, it is possible to provide a power converter capable of suppressing an increase in the voltage of a capacitor and operating even in an operation region in which a current is supplied to a power supply and current is supplied.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a power converter according to the present invention.

FIG. 2 is a detailed diagram of the voltage suppression circuit of FIG. 1;

FIG. 3 is a diagram showing a voltage suppression circuit according to a second embodiment of the power converter of the present invention.

FIG. 4 is a diagram showing a voltage suppression circuit according to a third embodiment of the power converter of the present invention.

FIG. 5 is a diagram showing a voltage suppression circuit according to a fourth embodiment of the power converter of the present invention.

FIG. 6 is a waveform chart showing the operation of the power converter shown in FIGS. 1 and 2 according to the present invention.

FIG. 7 is a configuration diagram showing an example of a conventional power converter.

8 is a waveform chart showing the operation of the conventional power converter of FIG.

[Explanation of symbols]

1. DC power supply, 2. DC reactor, 3. Converter, 4.
AC reactor, 5: AC power supply, 6: Voltage suppression circuit, 7
-18: reverse conducting GTO, 19-30: diode, 3
1-36 ... condenser, 37-42 ... diode, 43
... Capacitor, 44 ... Energy absorption circuit, 45 ... Converter AC power supply, 46 ... AC power supply, 47-52 ... Thyristor,
53: GTO, 54: resistor, 55 to 58: nonlinear resistance element.

Claims (1)

(57) [Claims] 1. A cathode of a first reverse conduction type self-extinguishing semiconductor device and an anode of a first diode are connected to form a first common connection point, and a cathode of a second diode and a second reverse conduction type are connected. Connect the anode of the self-extinguishing semiconductor device to the second
The first common connection point, one end of a capacitor is connected to the first common connection point, the other end of the capacitor is connected to the second common connection point, the first reverse conducting self-extinguishing semiconductor device A third common connection point where the anode of the second diode and the anode of the second diode are connected in common, and the cathode of the first diode and the cathode of the second reverse conducting self-extinguishing semiconductor element are connected in common. As the fourth common connection point,
In a power converter including a switch unit having the third common connection point and the fourth common connection point as terminals, when the voltage of the capacitor exceeds a predetermined value, the power flows into the capacitor. A power converter, comprising: a voltage suppressing unit that bypasses a current and suppresses a rise in the voltage of the capacitor.