JP2004153952A - Ac-ac direct conversion type power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a direct conversion type power converter which safely stops operation while protecting a switching element when abnormality occurs without complicating a circuit configuration, upsizing the apparatus, nor raising cost. <P>SOLUTION: An AC-AC direct conversion type power converter comprises a direct converter which directly converts an AC power to an AC power using a semiconductor switching element. There are provided an abnormality detecting means 46 that detects abnormality of the apparatus, all off pattern 48 and a switching switch 47 for releasing a load end by turning off all the switching elements in a direct converter 20' when an abnormality is detected by the abnormality detecting means 46, and a spike voltage suppressing circuit 251 to make the energy accumulated in the load 30 to be consumed by the switching element when the switching elements are turned off when detecting abnormality. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an AC-AC direct conversion type power converter that directly converts AC power to AC power without a large-sized energy buffer (hereinafter, simply referred to as a direct conversion type power converter as required), The present invention relates to a direct conversion type power conversion device having an enhanced protection function of a semiconductor switching element or the like 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, reference numeral 41 denotes voltage command generating means for generating a voltage command having a predetermined amplitude and frequency. Reference numeral 42 denotes 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 generation means for generating a switching pattern (PWM pattern) according to the following, 47 is a changeover switch, 10 is a power supply such as a three-phase AC power supply, 20 is a direct converter for performing AC-AC direct conversion, and 30 is an AC motor or the like. It is a load.
[0003]
Reference numeral 46 denotes an abnormality detecting means for detecting an abnormality such as output overcurrent, load temperature overheating, or cooling fan overheating and switching the changeover switch 47 to the abnormality processing side. Reference numeral 43 denotes a switching pattern at the time of abnormality detection. This is an abnormality processing unit that determines and outputs the result to the changeover 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 the bidirectional switches S1, S4, and S7 is connected to the input terminal R, each end of the bidirectional switches S2, S5, and S8 is connected to the input terminal S. Is connected to one end of each of the bidirectional switches S3, S6 and 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. And the other ends of the bidirectional switches S7 to S9 are collectively connected to the output terminal W, respectively.
[0005]
As shown in parentheses in FIG. 10, the bidirectional switches S1 to S9 connect semiconductor switching elements Sa and Sb, such as IGBTs, in which diodes Da and Db are connected in antiparallel, in anti-series, In this case, only the semiconductor switching elements Sa and Sb are connected in anti-parallel.
[0006]
In the direct converter 20 of this type, when the load 30 is an inductive load, when the load terminal is opened, a surge voltage is generated at both ends of the internal semiconductor switching element due to the energy stored in the reactor of the load 30, Destroy switching elements.
In order to prevent the destruction of the element due to the opening of the load end, in the direct conversion type power converter shown in FIG. 9, the power supply voltage and the load current are respectively detected, and the PWM generation means 42 changes the switching pattern according to their polarities. Generate and operate the converter 20 directly.
[0007]
At the same time, when the abnormality such as the output overcurrent described above is detected by the abnormality detecting means 46, the abnormality processing means 43 detects the phase having the maximum line voltage of the power supply voltage, and the load current of each phase is reduced. An abnormal switching pattern 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 by the direct converter 20 via the changeover switch 47 switched by the abnormality detecting means 46. Give to.
[0008]
That is, the converter 20 is directly driven by the switching pattern at the time of the abnormality to regenerate the load current to the power supply, and after the load current becomes zero, the switching elements of all the bidirectional switches S1 to S9 are turned off. For example, at the time of abnormality, the maximum line voltage on the power supply side is v _RS (line voltage between R phase and S phase), the U phase current i _U > 0, the V phase current i _V <0, and the W phase current i _W on the load side. 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 supply 10, and after the load current becomes zero, all the bidirectional switches S1 to S9 are turned off. The operation has been stopped.
[0009]
A drive control device that drives a synchronous motor using a matrix converter is described in, for example, Patent Document 1 described below.
Further, a power conversion device that directly drives an AC motor by directly converting an AC power supply voltage into an AC voltage having a different frequency and amplitude by using a PWM cycloconverter including a bidirectional switching unit is described in Patent Document 2 described below. This document discloses a technique for preventing destruction of a switching element due to charging and discharging of a snubber capacitor.
[0010]
[Patent Document 1]
JP-A-11-18489 (FIG. 1)
[Patent Document 2]
JP-A-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, a load pattern opening is dealt with by generating a regenerative mode pulse pattern according to a power supply voltage or a load current, so that the voltage detector 44 and the current detector 45 operate. If there is a defect or failure, abnormal processing is not properly performed, and there is a possibility that the switching element in the converter 20 is directly 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]
Further, in order to suppress the surge voltage, it is effective to provide a snubber circuit including a resistor, a diode, a capacitor, and the like. The configuration becomes complicated, resulting in an increase in the size of the device and an increase in cost.
[0013]
Further, the power conversion device described in Patent Document 2 has an object to prevent the destruction of the switching element. However, since a rectifying snubber circuit is an essential component, the circuit configuration is complicated as described above. In addition, there is a problem such as an increase in the size of the device and the size of the device, and in this conventional technique, no measures are taken to prevent the switching element from being destroyed due to a surge voltage generated when the load terminal is opened.
[0014]
Therefore, the present invention provides a direct conversion type power conversion device that can safely stop operation while protecting a switching element when an abnormality occurs without causing a complicated circuit configuration, an increase in size of the device, and an increase in cost. What you are trying to do.
[0015]
[Means for Solving the Problems]
In order to solve the above problem, an invention according to claim 1 is an AC-AC direct conversion type power converter including a direct converter that directly converts AC power into AC power using a semiconductor switching element.
Abnormality detection means for detecting an abnormality of the device;
Means for turning off all switching elements in the direct converter and opening a load end when an abnormality is detected by the abnormality detecting means;
When each switching element is turned off by the abnormality detection, a spike voltage suppressing means for causing the energy stored in the load to be consumed by the switching element;
It is provided with.
[0016]
The invention described in claim 2 is
In an AC-AC direct conversion type power converter including a direct converter that directly converts AC power into AC power using a semiconductor switching element,
Abnormality detection means for detecting an abnormality of the device;
When an abnormality is detected by the abnormality detecting means, an all-off pattern in which all switching elements in the direct converter are turned off to open the load terminal, and a load short-circuit pattern in which a predetermined switching element is turned on to short-circuit the load terminal. Means for alternately selecting
When each switching element is turned off by the abnormality detection, a spike voltage suppressing means for causing the energy stored in the load to be consumed by the switching element;
It is provided with.
[0017]
According to a third aspect of the present invention, in the AC-AC direct conversion type power converter according to the second aspect,
The switching element to be turned on by the load short-circuit pattern is changed with time.
[0018]
According to a fourth aspect of the present invention, in the AC-AC direct conversion type power converter according to the first, second or third aspect,
The spike voltage suppressing unit is a unit that repeatedly turns on and off the switching element by using a voltage applied to both ends of the switching element when the switching element is turned off, and clamps the voltage between both ends of the switching element to a substantially constant voltage. This spike voltage suppression means is composed of a series circuit of a Zener diode and a diode connected in reverse series to each other on the input side of a switching element such as an IGBT.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 shows a first embodiment of the present invention corresponding to claims 1 and 4, and the same components as those in FIG. 9 are denoted by the same reference numerals, and 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 changeover switch 47 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, the all-off pattern means that when the main part of the direct converter 20 'is constituted by the matrix converter 20 shown in FIG. 10, all of the bidirectional switches S1 to S9 (the switching elements constituting them) are turned off. This refers to 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 shown in FIG. 10, and the semiconductor switching elements (IGBT) S1a and S1b connected in anti-parallel in FIG. Similarly, 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 formed of a series circuit of a Zener diode 251 and a diode 252 are connected between the gate and collector of each of the switching elements S1a, S1b, S2a, S2b, S3a, S3b. These elements constitute a U-phase switching unit 20U.
[0022]
The configuration of the V-phase switching unit 20V and the W-phase switching unit 20W in FIG. 2 is the same as that of the above-described U-phase switching unit 20U, and the V-phase switching unit 20V includes switching elements S4a, S4b, S5a, S5b, S6a, S6b and these elements. And the W-phase switching unit 20W includes switching elements S7a, S7b, S8a, S8b, S9a, S9b and a spike voltage suppressing 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 (output terminal U on the load side). 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 operate so that the energy stored 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 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. Note that _ic is a collector current of the switching element, and _vce is a 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 turns on again.
[0026]
When the switching element S1a turns on, the collector-emitter voltage _vce decreases, so that the Zener diode 251 turns off, the gate voltage decreases, and the switching element S1a turns off. However, this turn-off operation, the collector of the switching element S1a - for emitter voltage v _ce rises again, the switching element S1a is turned on.
By repeating this process, the voltage across the switching element S1a resulting (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]
Hereinafter, the operation of this embodiment will be described.
First, in normal times, the changeover switch 47 is connected to the PWM generating means 42 side. The PWM generating means 42 generates a switching pattern according to the power supply voltage and the load current at that time based on the voltage command output from the voltage command generating means 41, and directly drives the converter 20 '.
[0028]
Next, an 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, or cooling fan overheating has occurred. In FIG. 4, S1 indicates an on / off command for the two switching elements S1a and S1b in FIG. 2. Hereinafter, S2, S3,... .
[0029]
In FIG. 4, the bidirectional switches S1, S5 and S8 are on until immediately before the occurrence of the abnormality. After the occurrence of the abnormality, the changeover switch 47 in FIG. The gate of S9 is turned off.
The load end is opened by the full gate off, and a large surge voltage is applied to both ends of the switching element. However, the energy stored in the inductance of the load 30 due to the operation of the above-described spike voltage suppression circuit causes a loss represented by the product of the collector-emitter voltage _vce of the switching element and the collector current _ic (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. Therefore, there is no possibility that the switching element is destroyed by the surge voltage.
[0030]
Next, FIG. 5 shows a second embodiment of the present invention corresponding to claims 2 and 4, in which the same components as those in FIG. 1 are denoted by the same reference numerals.
As described above, the energy stored in the reactor of the load 30 is consumed by 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 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, is to reduce the burden of the switching element and spike voltage suppression circuit.
[0032]
In the embodiment of FIG. 5, in addition to the all-off pattern 48, a load short-circuit pattern 49 for turning on a predetermined switching element to short-circuit the load end is provided.
The changeover switch 51 is driven by the output of the timer 50 to which the output of the abnormality detection means 46 is added, so that the all-off pattern 48 and the load short-circuit pattern 49 are switched. 20 '.
[0033]
The operation will be described. When the abnormality detecting means 46 detects an abnormality, the timer 50 starts measuring time, and the changeover switch 51 is switched at a predetermined time interval, so that the entire OFF period T _O (clamp period T _C ) and the load short-circuit period T _S by the load short-circuit pattern 49 are realized alternately. Then, when the changeover switch 51 is switched a predetermined number of times, the process finally shifts to the all-off pattern.
[0034]
FIG. 6 shows an ON / OFF command for 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 turned on and off intermittently, and then all the gates 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]
Next, FIG. 7 shows a third embodiment of the present invention according to claims 3 and 4.
In this embodiment, the load short-circuit pattern 52 includes three switching patterns of bidirectional switches S1, S4, S7 on, S2, S5, S8 on, S3, S6, S9 on, and keeps constant after an abnormality occurs. The load on each switching element and spike voltage suppression circuit is further reduced than in the second embodiment by changing the combination of bidirectional switches that are turned on for a period of time. Note that, similarly to the second embodiment, when switching is performed a predetermined number of times, the process finally shifts to the all-off pattern.
[0036]
FIG. 8 shows an ON / OFF command for each switching element when an abnormality occurs. In this example, the bidirectional switches S1, S5, and S8 are turned on at first, and after the occurrence of the abnormality, the timer 50 and the changeover switch 51 operate to turn off the full off period T _O and turn on the bidirectional switches S1, S4, and S7. load short-circuit period _{T S,} the whole oFF period _T O, S2, S5, S8 oN due to a load short circuit period _{T S,} the whole oFF period _{T O,} finally S3, S6, S9 and by load short period _{T S} is provided by, then Then, all gates are turned off to turn off all the bidirectional switches S1 to S8.
[0037]
According to the present embodiment, as is clear from the comparison with FIG. 6, it is possible to prevent the clamp period (off period) of a specific switching element from being long, and to distribute the off period to each switching element. The load on each switching element and the 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, the surge voltage applied to the switching element can be suppressed by the spike voltage suppressing means when the switching element is turned off and the load terminal is opened when an abnormality occurs, and the snubber resistance can be suppressed. The energy stored in the reactor of the load can be consumed by turning on and off the switching element without using such a method. Therefore, even if the voltage detector or the current detector fails, the operation of the device can be safely stopped without destroying the switching element of the main circuit.
Further, since no snubber circuit is required, the circuit configuration can be simplified and the device can be downsized.
[Brief description of the drawings]
FIG. 1 is a control block diagram showing a first embodiment of the present invention.
FIG. 2 is a configuration diagram of a direct converter in FIG.
FIG. 3 is a diagram illustrating a turn-off waveform of a switching element according to the first embodiment.
FIG. 4 is a timing chart showing the operation of the first embodiment.
FIG. 5 is a control block diagram showing a second embodiment of the present invention.
FIG. 6 is a timing chart showing the operation of the second embodiment.
FIG. 7 is a control block diagram illustrating a third embodiment of the present invention.
FIG. 8 is a timing chart showing the operation of the third embodiment.
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 to 206: Spike voltage suppression circuit 251: Zener diode 252: Diode 30: Load 41: Voltage command generation Means 42: PWM generating means 44: Voltage detector 45: Current detector 46: Abnormality detecting means 47, 51: Changeover switch 48: All off patterns 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 (4)

In an AC-AC direct conversion type power converter including a direct converter that directly converts AC power into AC power using a semiconductor switching element,
Abnormality detection means for detecting an abnormality of the device;
Means for turning off all switching elements in the direct converter and opening a load end when an abnormality is detected by the abnormality detecting means;
When each switching element is turned off by the abnormality detection, a spike voltage suppressing means for causing the energy stored in the load to be consumed by the switching element;
An AC-AC direct conversion type power converter, comprising: In an AC-AC direct conversion type power converter including a direct converter that directly converts AC power into AC power using a semiconductor switching element,
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 switching elements in the direct converter are turned off to open the load terminal, and a load short-circuit pattern in which a predetermined switching element is turned on to short-circuit the load terminal. Means for alternately selecting
When each switching element is turned off by the abnormality detection, a spike voltage suppressing means for causing the energy stored in the load to be consumed by the switching element;
An AC-AC direct conversion type power converter, comprising: The AC-AC direct conversion type power converter according to claim 2,
An AC-AC direct conversion type power converter, wherein a switching element to be turned on by the load short-circuit pattern is changed with time. The AC-AC direct conversion type power converter according to claim 1, 2, or 3,
The spike voltage suppressing unit is a unit that repeatedly turns on and off the switching element using a voltage applied to both ends of the switching element when the switching element is turned off, and clamps the voltage across the switching element to a substantially constant voltage. An AC-AC direct conversion power converter.

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