JP2000134945A - Power converting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent irregular heat generation of elements and surge current breakdown within a switching unit when a DC circuit termination occurs within a power converter. SOLUTION: In a power converting apparatus formed of a switching unit comprising a filter capacitor 3 and serial-connected semiconductor switching elements Q1, Q2, a diode 6 for surge current bypass is provided in inversely parallel to both ends of a serial body of a semiconductor switching element at the area near the switching unit 4 or within the switching unit. As a result, a vibration current flowing through the filter capacitor when a DC circuit termination is generated in the serial-connected body of semiconductor switching element may be branched with the diode for the surge current bypass and a surge current flowing through the diodes D1, D2 connected in inverse-parallel to the semiconductor switching element may be reduced to prevent irregular heat generation of element and surge current breakdown.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a power converter using a semiconductor switching element.

[0002]

2. Description of the Related Art Conventionally, a power conversion device in which semiconductor switching elements are connected in series as a two-level inverter and an AC output is obtained from a connection point has been widely known. FIG.
1 shows a circuit configuration of such a widely known power converter. This conventional power converter comprises a DC voltage source 1, a smoothing reactor 2 for the DC voltage source 1, a filter capacitor 3, a switching unit 4 in which semiconductor switching elements are configured in series, and a filter capacitor 3.
A wiring inductance 5 is shown in which the wiring inductance between the switching unit 4 and the switching unit 4 is concentrated. In the switching unit 4, two sets of semiconductor switching elements Q1 and Q2 connected in series are connected.
2; Diodes D1, D2; D3, D3 connected in antiparallel to Q3, Q4 and each semiconductor switching element.
4 are included.

Then, the semiconductor switching elements Q1, Q2
Are connected to the AC output terminals Ta and Tb, respectively, when the semiconductor switching elements Q1 and Q4 are simultaneously conducting, and when the semiconductor switching elements Q2 and Q3 are simultaneously By repeating the operation of supplying the DC voltage source 1 to the AC output terminals Ta and Tb in the conductive state, DC power is converted into AC power and output.

[0004]

However, such a conventional power converter has the following problems.
The semiconductor switching elements Q1 and Q2 or the semiconductor switching element Q forming a series body due to a device failure or the like.
When 3 and Q4 are simultaneously turned on, a short circuit occurs in the DC circuit, and the DC charges charged in the filter capacitor 3 flow into the short circuit. FIG. 10 shows a current waveform of the filter capacitor 3 at this time. The filter capacitor current after the occurrence of the DC short circuit is determined by the charging voltage, the impedance of the short circuit, and the capacity of the filter capacitor 3. Usually, since the resistance of the short circuit is small, the oscillating current is reduced as shown in FIG. Flows. The oscillating current shown in FIG. 10 is a diode D connected in antiparallel to the semiconductor switching elements Q1 to Q4, while a positive current (+ display) flows through the short circuit, while a negative current (−display) flows through the short circuit.
It flows by dividing into 1 to D4. Since the oscillation current continues to flow as the short circuit resistance decreases, the current in the negative direction flowing through the diodes D1 to D4 also flows repeatedly, which may cause abnormal heating of the diodes and destruction of the surge current.

In order to prevent this, if the surge current resistance and the cooling capacity of the diode in antiparallel with the semiconductor switching element are determined beforehand, diode destruction can be avoided, but there is a problem that the device becomes large. In the case of semiconductor switching elements, in which antiparallel diodes are housed in the same package as the semiconductor switching element, a large-capacity semiconductor switching element is required as compared to the device capacity, and the device is not enlarged. I can't.

On the other hand, there is an example in which a diode is connected in anti-parallel with the filter capacitor 3 in order to prevent reverse pressure of the electrolytic capacitor when an electric field capacitor or the like is used as the filter capacitor 3. In this case, since the diode is mounted closer to the filter capacitor 3 than the wiring inductance 5, the short-circuit current generated in the switching unit does not become oscillating, and the short-circuit current continues to flow. It may cause a widespread accident.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional technical problem. In a power converter having a semiconductor switching element connected in series, when a DC circuit short circuit occurs, a filter capacitor is provided. Surge current flowing through the diode connected in anti-parallel to the semiconductor switching element is reduced by the flowing oscillating current to prevent abnormal heating of the element and destruction of surge current. It is an object of the present invention to provide a power conversion device capable of preventing continuous flow in the power conversion device.

[0008]

According to a first aspect of the present invention, there is provided a power converter including a series body of semiconductor switching elements connected in series, wherein diodes are connected in anti-parallel to both ends of the series body of semiconductor switching elements. It was done.

According to a second aspect of the present invention, there is provided a power converter having a plurality of series-connected semiconductor switching elements connected in series, wherein diodes are connected in anti-parallel to both ends of each of the plurality of series-connected semiconductor switching elements. Connected.

In a third aspect of the present invention, there is provided a power conversion device having a plurality of series-connected semiconductor switching elements connected in series, and a plurality (but not all) of both ends of the series-connected semiconductor switching elements. , Respectively, in which diodes are connected in anti-parallel.

According to a fourth aspect of the present invention, there is provided a power conversion device comprising a plurality of series-connected semiconductor switching elements connected in series and a filter capacitor provided near the series-connected semiconductor switching elements. In the series body of the switching elements, diodes are connected in anti-parallel to both ends of the series body of the representative phase.

According to a fifth aspect of the present invention, there is provided a power conversion device comprising a plurality of series-connected semiconductor switching elements connected in series and a filter capacitor provided near each of the series-connected semiconductor switching elements. Diodes are connected in anti-parallel to both ends of each series body of semiconductor switching elements.

According to a sixth aspect of the present invention, there is provided a power conversion device comprising a plurality of series-connected semiconductor switching elements connected in series, and a filter capacitor provided near each of the series-connected semiconductor switching elements. And diodes are connected in anti-parallel to both ends of each of the series bodies of the plurality of semiconductor switching elements.

In the power converter according to the first to sixth aspects of the present invention, a diode for surge current bypass is connected in anti-parallel to both ends of each series body of semiconductor switching elements, so that the series body of semiconductor switching elements is connected. When a short circuit occurs in the DC circuit, the oscillating current flowing through the filter capacitor is shunted by the surge current bypass diode, and the surge current flowing through the diode connected in anti-parallel with the semiconductor switching element is reduced, resulting in abnormal heat generation of the element. Prevent surge current breakdown.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a circuit configuration of the first embodiment of the present invention. In the power converter of the first embodiment, the same parts as those of the circuit configuration of the conventional example shown in FIG. 9 are denoted by the same reference numerals. The feature of the first embodiment resides in that a diode 6 for surge current bypass is provided close to the semiconductor switching unit 4.

Here, if the semiconductor switching elements Q1 and Q2 are simultaneously turned on (or the semiconductor switching elements Q3 and Q4 are simultaneously turned on) due to a failure of the device or the like, a DC circuit short circuit occurs and the filter capacitor is turned off. The charged DC charge flows into the short circuit. FIG. 2 shows a current waveform example of the filter capacitor 3 at this time. The filter capacitor current after a DC short circuit occurs is determined by the charging voltage, the impedance of the short circuit, and the filter capacitor capacity.
An oscillating current flows because the resistance of the short circuit is small.

The positive current (+ display) of the oscillating current waveform shown in FIG. 2 flows through the short circuit, but the negative current flows in antiparallel to the surge current bypass diode 6 and the semiconductor switching elements Q1 to Q4. Connected diodes D1
It is split and flows to D4. Here, diodes D1 to D4 connected in anti-parallel to semiconductor switching elements Q1 to Q4
On the one hand, the current flows through the series circuit of diodes D1 and D2, and the other flows through the series circuit of diodes D3 and D4. 3
Most of the current in the negative direction of the oscillating current flows through the surge current bypass diode 6, as indicated by the hatched portion in FIG. 2, so that the currents of the diodes D1 to D4 can be sufficiently reduced.

Next, a second embodiment of the present invention will be described with reference to FIG.
It will be described based on. In the circuit configuration of the second embodiment, the same parts as those of the conventional circuit elements shown in FIG. 8 are denoted by the same reference numerals. The feature of the second embodiment is that a diode 6 for surge current bypass is provided.
A and 6B are connected to the series body of the semiconductor switching elements Q1 and Q2 and the series body of the semiconductor switching elements Q3 and Q4, respectively, in the switching unit 4 at both ends at positions near them.

In the circuit configuration of the second embodiment, surge current bypass diodes 6A and 6B are installed in the immediate vicinity of a series body of semiconductor switching elements Q1 and Q2 and a series body of semiconductor switching elements Q3 and Q4. Thereby, as compared with the circuit configuration of the first embodiment shown in FIG. 1, the currents of the diodes D1 to D4 connected in anti-parallel to the semiconductor switching elements Q1 to Q4 can be further reduced, and a surge current bypass can be provided. Since there are two diodes (6A, 6B), it can be composed of relatively small diodes.

FIG. 4 shows a circuit configuration in which the present invention is applied to a three-phase bridge inverter circuit configuration as another example of the second embodiment. Also in this example, the same components as those in the circuit configuration shown in FIG. 3 are denoted by the same reference numerals. In the circuit configuration of FIG. 4, three-phase semiconductor switching elements Q1, Q2; Q3, Q4; Q5, and Q6 in the switching unit 4 of the three-phase bridge inverter circuit are close to each other in series, and antiparallel to both ends thereof. Are connected to diodes 6A, 6B and 6C for surge current bypass.

The power converter having the configuration shown in FIG. 4 has the same effect as the power converter shown in FIG. 3, and reduces the current of diodes D1 to D6 connected in antiparallel to semiconductor switching elements Q1 to Q6. And a surge current bypass diode for three circuits (6A, 6B,
6C), it can be composed of a relatively small diode.

Next, a third embodiment of the present invention will be described with reference to FIG.
It will be described based on. In the circuit configuration of FIG. 5, the same components as those of the second embodiment shown in FIG. 3 are denoted by the same reference numerals. The feature of the third embodiment resides in that the number of diodes provided for surge current bypass is smaller than the number of series-connected semiconductor switching elements provided in the switching unit 4 in series.

In the case of the embodiment shown in FIG. 5, in the switching unit 4 of the three-phase bridge inverter circuit, a series body of two-phase semiconductor switching elements, ie, the semiconductor switching of the phase closest to the filter capacitor 3 A series body of the elements Q1 and Q2 and a series body of the semiconductor switching elements Q5 and Q6 of the farthest phases are respectively selected as representatives, and diodes 6A and 6B for surge current bypass are connected in close proximity and antiparallel. .

Also in this embodiment, the surge current bypass diodes 6A and 6B can reduce the number of diodes and reduce the size. Also, as in the first and second embodiments, the filter capacitor 3 can be used. Most of the current in the negative direction of the oscillating current is a diode 6 for surge current bypass.
Since the current flows through A and 6B, the current of the diodes D1 to D6 can be sufficiently reduced.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In the circuit configuration of FIG. 6, the same elements as those of the circuit configurations shown in FIGS. 4 and 5 are denoted by the same reference numerals. The power converter according to the fourth embodiment includes a filter capacitor 3A, 3B, 3C for a series body of semiconductor switching elements of each phase constituting a three-phase bridge inverter circuit in a switching unit 4.
And a surge current bypass diode 6 is provided in anti-parallel with one phase of a series body of these semiconductor switching elements as a representative phase.

In the case of the fourth embodiment, a plurality of filter capacitors 3, 3A, 3
Although a short-circuit current flows from B and 3C, a surge current in the negative direction also flows through diodes D1 to D6 connected in antiparallel to semiconductor switching elements Q1 to Q6. This current is
One flows through a series circuit of diodes D1 and D2 and a series circuit of diodes D3 and D4.
5 and D6, the current of the diode 6 for surge current bypass, which naturally has no series configuration, increases, and a series body of diodes (D1-D2) connected in the opposite direction to the semiconductor switching element of each phase. , D3-D4
D5 to D6) can be reduced.

Next, a fifth embodiment of the present invention will be described with reference to FIG. In the power converter shown in FIG.
The same components as those of the power converter according to the fourth embodiment shown in FIG. 6 are denoted by the same reference numerals. Fifth
The feature of this embodiment is that a three-phase bridge inverter configuration in which filter capacitors 3A, 3B, and 3C are installed in each phase in the switching unit 4 is provided in parallel with each of the two-phase filter capacitors. A diode 6 for bypassing a surge current in antiparallel and close to a series body (Q1-Q2, Q3-Q4) of semiconductor switching elements.
A and 6B are connected.

That is, the surge current bypass diode 6A is connected in anti-parallel to both ends of the series body of the semiconductor switching elements Q1 and Q2 at a position between the filter capacitors 3A and 3B, and the surge current bypass diode 6B is At a position between the filter capacitors 3B and 3C, the semiconductor switching elements Q3 and Q4 are connected in anti-parallel to both ends of the series body.

Also in the case of the fifth embodiment, the surge current in the negative direction flowing through the diodes D1 to D6 connected in antiparallel to the semiconductor switching elements Q1 to Q6 can be reduced, and the surge current bypass diode 6A , 6
As B, a diode smaller than that of the fourth embodiment shown in FIG. 6 can be used.

Next, a sixth embodiment of the present invention will be described with reference to FIG.
It will be described based on. In the power converter illustrated in FIG. 8, the same components as those of the power converter according to the fifth embodiment illustrated in FIG. 7 are denoted by the same reference numerals. The power converter according to the sixth embodiment is characterized in that diodes 6A, 6B and 6C for surge current bypass are provided in each of the three phases with respect to the power converter according to the fifth embodiment shown in FIG. It is in the point which did.

That is, the surge current bypass diode 6A is connected in anti-parallel to both ends of the series body of the semiconductor switching elements Q1 and Q2 at a position between the filter capacitors 3A and 3B, and the surge current bypass diode 6B is At the position between the filter capacitors 3B and 3C, the semiconductor switching elements Q3 and Q4 are connected in anti-parallel to both ends of the series body, and the surge current bypass diode 6C is connected to the semiconductor switching elements Q5 and Q6 more than the filter capacitor 3C. The semiconductor switching elements Q5 and Q6 are connected in anti-parallel to the series body at a position close to the series body.

Also in the sixth embodiment, the surge current in the negative direction flowing through the diodes D1 to D6 connected in antiparallel to the semiconductor switching elements Q1 to Q6 can be reduced, and the surge current bypass diode 6A , 6
As B and 6C, smaller diodes can be used than those of the fifth embodiment shown in FIG.

[0033]

As described above, according to the first to sixth aspects of the present invention, a surge current bypass diode is connected in anti-parallel to both ends of each series body of semiconductor switching elements, so that the series of semiconductor switching elements are connected in series. When a DC circuit short circuit occurs in the body, the oscillating current flowing through the filter capacitor is shunted by this surge current bypass diode, and the surge current flowing through the diode connected in anti-parallel with the semiconductor switching element is reduced, causing the element to malfunction. Heat generation and surge current destruction can be prevented beforehand, the device can be prevented from being enlarged, and short-circuit current can be prevented from continuously flowing without vibration.

[Brief description of the drawings]

FIG. 1 is a circuit diagram according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram illustrating an effect of reducing an oscillating current flowing in a series short circuit of the semiconductor switching element according to the embodiment.

FIG. 3 is a circuit diagram according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram of another example of the second embodiment.

FIG. 5 is a circuit diagram according to a third embodiment of the present invention.

FIG. 6 is a circuit diagram according to a fourth embodiment of the present invention.

FIG. 7 is a circuit diagram according to a fifth embodiment of the present invention.

FIG. 8 is a circuit diagram according to a sixth embodiment of the present invention.

FIG. 9 is a circuit diagram of a conventional example.

FIG. 10 is a waveform diagram showing an oscillating current flowing in a series short circuit of a semiconductor switching element in a conventional example.

[Explanation of symbols]

Reference Signs List 1 DC voltage power supply 2 Smoothing reactor 3, 3A, 3B, 3C Filter capacitor 4 Switching unit 5 Wiring inductance 6, 6A, 6B, 6C Surge current bypass diode Q1-Q6 Semiconductor switching element D1-D6 Diode Ta-Tc AC output Terminal

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H007 AA17 CA01 CB02 CB04 CB05 CC07 CC23 FA03 FA06 FA13 FA20 5H740 AA08 BA11 BB05 BB09 MM04 MM05

Claims (6)

[Claims] 1. A power converter comprising a series body of semiconductor switching elements connected in series, wherein diodes are connected in anti-parallel to both ends of the series body of semiconductor switching elements. 2. A power converter comprising a plurality of series-connected semiconductor switching elements connected in series, wherein diodes are connected in anti-parallel to both ends of each of the series-connected semiconductor switching elements. Power converter. 3. A power conversion device comprising a plurality of series-connected semiconductor switching elements connected in series, wherein a diode is provided at each of some (but not all) ends of the series-connected semiconductor switching elements. A power converter, wherein the power converter is connected in anti-parallel. 4. A power converter comprising a plurality of series-connected semiconductor switching elements connected in series and a filter capacitor provided in the vicinity of the series-connected semiconductor switching elements, wherein the series-connected plurality of semiconductor switching elements is provided. A power converter, wherein a diode is connected in anti-parallel to both ends of a series body of a representative phase. 5. A power converter comprising a plurality of serially connected semiconductor switching elements in series and a filter capacitor provided near each of said serially connected semiconductor switching elements, wherein a series connection of said plurality of semiconductor switching elements is provided. A power converter wherein diodes are connected in anti-parallel to both ends of each body. 6. A power converter comprising a plurality of series-connected semiconductor switching elements connected in series, and a filter capacitor provided in the vicinity of each of the series-connected semiconductor switching elements, wherein: A power converter, wherein diodes are connected in anti-parallel to both ends of each of the series bodies of the plurality of semiconductor switching elements.