JP4042531B2 - AC-AC direct conversion power converter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an AC-AC direct conversion type power converter (hereinafter simply referred to as a direct conversion type power converter if necessary) that directly converts AC power into AC power without a large energy buffer. The present invention relates to a direct conversion type power conversion device having an enhanced protection function such as a semiconductor switching element at the time of occurrence.
[0002]
[Prior art]
FIG. 9 is a control block diagram of a conventional direct conversion type power converter having a processing function when an abnormality occurs.
In FIG. 9, 41 is a voltage command generating means for generating a voltage command having a predetermined amplitude and frequency, and 42 is a power supply voltage detected by a voltage detector 44 and a load current detected by a current detector 45 based on the voltage command. PWM generating means for generating a switching pattern (PWM pattern) according to the above, 47 is a changeover switch, 10 is a power source such as a three-phase AC power supply, 20 is a direct converter that performs AC-AC direct conversion, 30 is an AC motor or the like It is a load.
[0003]
Further, 46 is an abnormality detecting means for detecting an abnormality such as output overcurrent, load temperature overheating, cooling fan overheating, etc. and switching the changeover switch 47 to the abnormality processing side, and 43 is a switching pattern at the time of abnormality detection. This is an abnormality processing means for determining and outputting to the selector switch 47 side.
[0004]
Here, a typical example of the direct converter 20 is a matrix converter shown in FIG. That is, in FIG. 10, one end of each of bidirectional switches S1, S4, S7 is connected to the input terminal R, one end of each of bidirectional switches S2, S5, S8 is connected to the input terminal S, and Is connected to one end of each of the bidirectional switches S3, S6, S9. The other ends of the bidirectional switches S1 to S3 are collectively connected to the output terminal U, and the other ends of the bidirectional switches S4 to S6 are collectively connected. The other ends of the bidirectional switches S7 to S9 are connected to the output terminal W in a lump.
[0005]
As shown in parentheses in FIG. 10, the bidirectional switches S1 to S9 connect semiconductor switching elements Sa and Sb, such as IGBTs, to which diodes Da and Db are connected in reverse parallel, in reverse series or have reverse breakdown voltage capability. If there is, only the semiconductor switching elements Sa and Sb are connected in antiparallel.
[0006]
In this type of direct converter 20, when the load 30 is an inductive load, when the load end is opened, a surge voltage is generated at both ends of the internal semiconductor switching element due to the energy accumulated in the reactor of the load 30, Destroy the switching element.
In order to prevent the destruction of the element due to such opening of the load end, the direct conversion type power conversion device of FIG. 9 detects the power supply voltage and the load current, respectively, and the PWM generating means 42 changes the switching pattern according to these polarities. Generating and operating the converter 20 directly.
[0007]
At the same time, when the abnormality such as the output overcurrent described above is detected by the abnormality detection means 46, the abnormality processing means 43 detects the phase that is the maximum line voltage of the power supply voltage, and the load current of each phase is detected. A switching pattern at the time of abnormality for the direct converter 20 is determined so as to regenerate to the phase having the maximum line voltage, and this switching pattern is directly converted via the changeover switch 47 switched by the abnormality detecting means 46. To give.
[0008]
That is, the converter 20 is directly driven by the switching pattern at the time of abnormality to regenerate the load current to the power source, and after the load current becomes zero, the switching elements of all the bidirectional switches S1 to S9 are turned off. For example, when an abnormality occurs, the maximum line voltage on the power supply side is v _RS (R-phase to S-phase line voltage), U-phase current i _U > 0 on the load side, V-phase current i _V <0, and W-phase current i _W If it is <0, the bidirectional switches S2, S4, and S7 in FIG. 10 are turned on to regenerate the load current to the power source 10, and all the bidirectional switches S1 to S9 are turned off after the load current becomes zero. Operation has stopped.
[0009]
In addition, the drive control apparatus which drives a synchronous motor using a matrix converter is described in patent document 1 mentioned later, for example.
In addition, a power converter that drives an AC motor by directly converting an AC power supply voltage into an AC voltage having a different frequency and amplitude by a PWM cycloconverter including a bidirectional switching means is described in Patent Document 2 described later. This document discloses a technique for preventing the switching element from being destroyed due to charging / discharging of the snubber capacitor.
[0010]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-18489 (FIG. 1)
[Patent Document 2]
Japanese Patent Application Laid-Open No. 11-262264 (FIGS. 1, 6 to 8, [0010], [0015] to [0017])
[0011]
[Problems to be solved by the invention]
In the prior art shown in FIG. 9, since the load end opening is dealt with by generating a regenerative mode pulse pattern according to the power supply voltage and the load current, the voltage detector 44 and the current detector 45 are operated. If there is a defect or failure, the abnormal process is not properly performed, and the switching element in the direct converter 20 may be destroyed.
Further, if all the bidirectional switches are simply cut off regardless of the magnitude of the load current, the load end is opened, and a large surge voltage is applied to the switching element.
[0012]
Furthermore, in order to suppress the surge voltage, it is effective to provide a snubber circuit composed of a resistor, a diode, a capacitor, etc., but providing these snubber circuits only for the purpose of dealing with an abnormality is a circuit. The configuration becomes complicated, leading to an increase in size and cost of the apparatus.
[0013]
In addition, the power conversion device described in Patent Document 2 has a problem of preventing the destruction of the switching element. However, since the rectifying snubber circuit is an essential component, the circuit configuration is complicated as described above. In addition to problems such as increase in size and size of the apparatus, in this conventional technique, measures for preventing the destruction of the switching element due to the surge voltage generated when the load end is opened are not studied.
[0014]
Accordingly, the present invention provides a direct conversion type power conversion device that can safely stop operation while protecting a switching element in the event of an abnormality without incurring complicated circuit configuration, large device size, and cost increase. It is something to try.
[0015]
[Means for Solving the Problems]
In order to solve the above-described problem, the invention described in claim 1 is an AC-AC direct conversion type power conversion device including a direct converter that directly converts AC power into AC power using a semiconductor switching element.
An abnormality detection means for detecting an abnormality of the device;
When an abnormality is detected by the abnormality detection means, an all-off pattern in which all the switching elements in the direct converter are turned off to open the load end, and a predetermined switching element in the direct converter is turned on to turn off the load end. Means for alternately selecting a load short-circuit pattern to be short-circuited ;
Spike voltage suppression means for consuming the energy accumulated in the load by the switching element when each switching element is turned off by abnormality detection;
Equipped with a,
A combination of switching elements to be turned on by the load short-circuit pattern is changed with time .
[0018]
The invention described in claim 2 is the AC-AC direct conversion power converter according to claim 1 ,
The spike voltage suppression means is means for repeatedly turning on and off the switching element by using a voltage applied to both ends when the switching element is turned off, and clamping the voltage across the switching element to a substantially constant voltage. The spike voltage suppression means is constituted by a series circuit of a Zener diode and a diode connected in anti-series with each other on the input side of a switching element such as an IGBT, for example.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 shows a first reference embodiment of the present invention. The same components as those of FIG. 9 are denoted by the same reference numerals and the description thereof will be omitted. Hereinafter, different parts will be mainly described.
[0020]
The configuration of FIG. 1 differs from that of FIG. 9 in that the configuration of the direct converter 20 ′ and the selector switch 47 that is switched by the output of the abnormality detection means 46 are switched to the all-off pattern 48 side in the event of an abnormality. Here, when the main part of the direct converter 20 ′ is constituted by the matrix converter 20 shown in FIG. 10, the all-off pattern means that all the bidirectional switches S1 to S9 (switching elements constituting them) are turned off. This is the switching pattern to be performed.
[0021]
First, the configuration of the direct converter 20 ′ will be described with reference to FIG.
The basic circuit of the direct converter 20 ′ shown in FIG. 2 is the same as that of the matrix converter 20 of FIG. 10, and the bidirectional switching S1 of FIG. 10 is performed by the semiconductor switching elements (IGBTs) S1a and S1b connected in antiparallel in FIG. However, S2a and S2b in FIG. 2 constitute S2 in FIG. 10 and S3a and S3b in FIG. 2 constitute S3 in FIG.
Further, in FIG. 2, spike voltage suppression circuits 201 to 206 each consisting of a series circuit of a Zener diode 251 and a diode 252 are connected between the gates and collectors of the switching elements S1a, S1b, S2a, S2b, S3a, and S3b. These elements constitute the U-phase switching unit 20U.
[0022]
The configurations of the V-phase switching unit 20V and the W-phase switching unit 20W in FIG. 2 are also the same as the U-phase switching unit 20U described above. The V-phase switching unit 20V includes switching elements S4a, S4b, S5a, S5b, S6a, S6b and these The W-phase switching unit 20W is composed of switching elements S7a, S7b, S8a, S8b, S9a, S9b and a spike voltage suppression circuit between these gates and collectors. .
In FIG. 2, the internal configurations of the V-phase switching unit 20V and the W-phase switching unit 20W are not shown for convenience.
[0023]
Here, taking the U-phase switching unit 20U as an example, the spike voltage suppression circuits 201 to 206 connect the cathodes of the Zener diode 251 and the diode 252, and the anode of the Zener diode 251 is connected to the gate of the switching element. The anode of the diode 252 is connected to the collector of the switching element (load-side output terminal U). The connection configuration of the spike voltage suppression circuit is the same for the other V-phase switching unit 20V and W-phase switching unit 20W.
[0024]
The spike voltage suppression circuits 201 to 206 act so that the energy accumulated in the reactor of the load 30 is consumed by the switching element, and the spike voltage generated when the switching element is turned off is suppressed by the breakdown of the Zener diode 251. .
[0025]
FIG. 3 shows a turn-off waveform of the switching element when there is a spike voltage suppression circuit. Here, _ic is the collector current of the switching element, and v _ce is the collector-emitter voltage.
For example, the spike voltage suppression circuit 201 in FIG. 2, the collector at turn-off of the switching elements S1a - when the voltage exceeds the Zener voltage V _z between the emitter occurs, the Zener diode 251 is turned on, voltage to the gate is applied The switching element S1a is turned on again.
[0026]
When the switching element S1a is turned on, the collector-emitter voltage v _ce decreases, so that the Zener diode 251 is turned off, and the gate voltage is reduced to turn off. However, since this turn-off operation causes the collector-emitter voltage v _ce of the switching element S1a to rise again, the switching element S1a is turned on.
By repeating this process, as a result, the voltage across the switching element S1a (emitter-collector voltage v _ce ) is clamped to the Zener voltage V _z of the Zener diode 251. Shown as T _C the clamp period in FIG.
[0027]
The operation of this reference embodiment will be described below.
First, during normal operation, the changeover switch 47 is connected to the PWM generating means 42 side. Based on the voltage command output from the voltage command generation means 41, the PWM generation means 42 generates a switching pattern corresponding to the power supply voltage and load current at that time and directly drives the converter 20 ′.
[0028]
Next, the operation when an abnormality occurs will be described. FIG. 4 shows an example of an on / off command for each switching element when an abnormality such as output overcurrent, load temperature overheating, cooling fan overheating, or the like occurs. In FIG. 4, S1 indicates an on / off command for the two switching elements S1a and S1b in FIG. 2, and hereinafter, S2, S3,. .
[0029]
In FIG. 4, the bidirectional switches S1, S5, and S8 are on until immediately before the occurrence of the abnormality, and after the abnormality occurs, the changeover switch 47 in FIG. 1 is switched to the all-off pattern 48 side and all the bidirectional switches S1 to S1. The gate of S9 is turned off.
When all the gates are turned off, the load end is opened, and a large surge voltage is applied to both ends of the switching element. However, due to the operation of the spike voltage suppression circuit described above, the energy accumulated in the inductance of the load 30 is a loss represented by the product of the collector-emitter voltage v _ce and the collector current _ic of the switching element (the hatched line in FIG. 3). consumed by parts), the voltage across the switching device is clamped to the Zener voltage V _z across clamp period T _C. For this reason, there is no possibility that the switching element is destroyed by the surge voltage.
[0030]
Next, FIG. 5 shows a second reference embodiment of the present invention, and the same reference numerals are assigned to the same components as those in FIG.
As described above, the energy stored in the reactor of the load 30 is consumed due to the loss of the switching element. Therefore, the energy stored in the reactor of the load 30 once the clamp period T _C becomes long if very large, there is a risk of destroying the switching element and spike voltage suppression circuit.
[0031]
Therefore, in this reference embodiment, when the energy stored in the reactor of the load 30 is consumed by the switching element, a period in which the switching element is completely turned off and a period in which the load terminal is short-circuited (a period in which the output voltage is zero) are repeated. I did it. That is, by intermittently across the load short period without continuously clamp period T _C, it is to reduce the burden of the switching element and spike voltage suppression circuit.
[0032]
In addition to the all-off pattern 48, the reference form of FIG. 5 includes a load short-circuit pattern 49 for turning on a predetermined switching element to short-circuit the load end.
Then, by driving the changeover switch 51 by the output of the timer 50 to which the output of the abnormality detection means 46 is applied, the all-off pattern 48 and the load short-circuit pattern 49 are changed over, and the selected pattern is directly converted through the changeover switch 47. It is comprised so that it may add to 20 '.
[0033]
The operation will be described. When the abnormality detection means 46 detects an abnormality, the timer 50 starts measuring time, and the changeover switch 51 is switched at a predetermined time interval, whereby the all-off period T _O (clamp period T _C) to achieve alternately the load short period T _S due to the load short-circuit pattern 49. Then, after the changeover switch 51 is switched a predetermined number of times, the process finally proceeds to the all-off pattern.
[0034]
FIG. 6 shows an on / off command of each switching element when an abnormality occurs. In this example, initially, the bidirectional switch S1, S5, S8 are turned on, after the abnormality occurrence is repeatedly and full off period T _O load shorted period T _S by the operation of the timer 50 and switch 51 alternately The bidirectional switches S1, S4, and S7 are intermittently turned on and off, and then all the gate switches are turned off to turn off all the bidirectional switches S1 to S8.
Accordingly, if a very large energy stored in the reactor in the clamp period T _C of the load 30 is prevented from being prolonged, it is possible to prevent the breakdown of the switching element and spike voltage suppression circuit.
[0035]
Then, Figure 7 shows the implementation form of the present invention.
In this embodiment, the load short-circuit pattern 52 includes three switching patterns, that is, bidirectional switches S1, S4, S7 are turned on, S2, S5, S8 are turned on, and S3, S6, S9 are turned on. period on which the combination of the bidirectional switch by causing over time change, and the burden of the switching elements and spike voltage suppression circuit and so even reduce than the second reference embodiment. As in the second reference embodiment, after switching a predetermined number of times, the process finally shifts to an all-off pattern.
[0036]
FIG. 8 shows an on / off command of each switching element when an abnormality occurs. In this example, initially, the bidirectional switch S1, S5, S8 are turned on, after the abnormality occurs by operation of the timer 50 and switch 51, the whole OFF period _{T O,} the bidirectional switch S1, S4, S7 ON A load short-circuit period T _S , a total off-period T _O , a load short-circuit period T _S by turning on S2, S5 and S8, a total off-period T _O , and finally a load short-circuit period T _S by S3, S6 and S9 are provided. Then, all the gate switches S1 to S8 are turned off, and all the gates are turned off.
[0037]
According to the present embodiment, as is clear from comparison with FIG. 6, it is possible to prevent the clamp period (off period) of a specific switching element from extending for a long time and to distribute the off period to each switching element. The burden on each switching element and spike voltage suppression circuit can be further reduced and the life can be extended.
[0038]
【The invention's effect】
As described above, according to the present invention, when the switching element is turned off and the load end is opened when an abnormality occurs, the surge voltage applied to the switching element can be suppressed by the spike voltage suppressing means, and the snubber resistance The energy stored in the reactor of the load can be consumed by turning on / off the switching element without using the above. For this reason, even if a voltage detector or a current detector fails, the operation of the apparatus can be safely stopped without destroying the switching elements of the main circuit.
Further, since the snubber circuit is unnecessary, the circuit configuration can be simplified and the apparatus can be downsized.
[Brief description of the drawings]
FIG. 1 is a control block diagram showing a first reference embodiment of the present invention.
FIG. 2 is a configuration diagram of a direct converter in FIG. 1;
FIG. 3 is a diagram showing a turn-off waveform of a switching element in the first reference embodiment.
FIG. 4 is a timing chart showing the operation of the first reference embodiment.
FIG. 5 is a control block diagram showing a second reference embodiment of the present invention.
FIG. 6 is a timing chart showing the operation of the second reference embodiment.
7 is a control block diagram showing an implementation form of the present invention.
FIG. 8 is a timing chart showing the operation of the embodiment of the present invention .
FIG. 9 is a control block diagram showing a conventional technique.
FIG. 10 is a configuration diagram of a matrix converter.
[Explanation of symbols]
10: Power supply 20 ′: Direct converter 20U: U-phase switching unit 20V: V-phase switching unit 20W: W-phase switching units 201-206: Spike voltage suppression circuit 251: Zener diode 252: Diode 30: Load 41: Voltage command generation Means 42: PWM generation means 44: Voltage detector 45: Current detector 46: Abnormality detection means 47, 51: Changeover switch 48: All-off pattern 49, 52: Load short-circuit pattern 50: Timers S1a, S1b, S2a, S2b, S3a, S3b, S4a, S4b, S5a, S5b, S6a, S6b, S7a, S7b, S8a, S8b, S9a, S9b: Semiconductor switching elements

Claims (2)

In an AC-AC direct conversion type power conversion device including a direct converter that directly converts AC power into AC power using a semiconductor switching element,
An abnormality detection means for detecting an abnormality of the device;
When an abnormality is detected by the abnormality detection means, an all-off pattern in which all the switching elements in the direct converter are turned off to open the load end, and a predetermined switching element in the direct converter is turned on to turn off the load end. Means for alternately selecting a load short-circuit pattern to be short-circuited ;
Spike voltage suppression means for consuming the energy accumulated in the load by the switching element when each switching element is turned off by abnormality detection;
Equipped with a,
An AC-AC direct conversion type power conversion device, wherein a combination of switching elements to be turned on by the load short-circuit pattern is changed over time . In the AC-AC direct conversion type power converter according to claim 1,
The spike voltage suppression means is means for repeatedly turning on and off the switching element by using a voltage applied to both ends when the switching element is turned off, and clamping the voltage across the switching element to a substantially constant voltage. AC-AC direct conversion type power converter characterized by the above.

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