JP2004254360A - Backup device of ac-ac power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backup device having a low cost and a small size by enabling continuous operation even when a power supply is abnormal or when a semiconductor switch fails in operation. <P>SOLUTION: An AC-AC power converter includes a matrix converter for converting a polyphase AC voltage into a polyphase AC voltage via a virtual rectifier and a virtual inverter. The AC-AC power converter synthesizes control pulses to the virtual rectifier and the virtual inverter and imparts the synthesized pulse to the matrix converter. The AC-AC converter further includes a power supply fault detecting means 70 for detecting the fault of the polyphase AC voltage of the power supply side, a changeover switch 80, a DC power supply 83 for supplying a DC voltage to the input side of the virtual rectifier instead of the polyphase AC voltage supplied to the virtual rectifier, and a rectifier control means 40 for turning on the predetermined semiconductor switch and turning off the other semiconductor switch according to a switch-on command so that the DC voltage is present at the virtual DC link of the matrix converter 30. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides an AC-AC power converter that directly converts a multi-phase AC voltage to a multi-phase AC voltage using a matrix converter, even when a power failure occurs or when a semiconductor switch forming the matrix converter fails. The present invention relates to a backup device for continuing operation without any change.
[0002]
[Prior art]
FIG. 4 shows a configuration of a conventional AC-AC power converter using a matrix converter. Here, the most common three-phase is illustrated as an example of the input-side and output-side polyphases of the matrix converter. Each phase on the input side (power supply side) and the AC input terminals are denoted by R, S, T, and the output. Side (load side) and the AC output terminal are U, V, W.
[0003]
4, reference numeral 10 denotes a three-phase AC power supply, reference numeral 20 denotes a three-phase uninterruptible power supply connected to the three-phase AC power supply 10, reference numeral 30 denotes a connection between the AC input terminals R, S, T and the AC output terminals U, V, W. Is a matrix converter composed of bidirectional semiconductor switches 31 to 39 connected to the matrix converter.
Here, the semiconductor switches 31 to 39 are configured by connecting two semiconductor switching elements, such as IGBTs, in series in the reverse direction, and connecting a freewheel diode to each switching element in anti-parallel.
[0004]
In controlling the matrix converter 30, a virtual rectifier 30A and a virtual inverter 30B are assumed in the matrix converter 30 (see FIG. 5), and PWM pulses (switching functions) for these are rectified by the rectifier control means 40 and the inverter control means in FIG. A method is known in which both the PWM pulses are created by the PWM converter 50 and the two PWM pulses are combined by the PWM pulse combining means 60 and given to the matrix converter 30. See Satoe, Isao Takahashi, IEEJ Semiconductor Power Conversion Study Group, SPC-01-121, IEA-01-64).
[0005]
On the virtual rectifier 30A side, the rectifier control means 40 compares the input current command with the carrier waveform, generates a PWM pulse on the rectifier 30A side according to the magnitude relationship, and on the virtual inverter 30B side, the inverter control means 50 The output voltage command is compared with the carrier waveform, and a PWM pulse on the inverter 30B side is generated based on the magnitude relationship. By synthesizing these PWM pulses and driving the semiconductor switches 31 to 39 of the matrix converter 30, the input current and the output voltage are controlled as instructed.
Here, the operation of the virtual rectifier 30A is equivalent to an operation of a current-type PWM rectifier because a power supply short circuit is not allowed.
[0006]
Since the matrix converter 30 does not include a large-sized energy buffer including a smoothing capacitor and a reactor, the operation must be stopped when a power failure such as a power failure, a voltage drop, or a significant voltage imbalance occurs. . However, like an elevator or an industrial plant, depending on the application, continuous operation may be required even when a power failure occurs without stopping the apparatus as much as possible.
Therefore, in order to cope with a power failure, the prior art in FIG. 4 includes a three-phase uninterruptible power supply 20 between the three-phase AC power supply 10 and the matrix converter 30. As a result, even if an abnormality occurs in the three-phase AC power supply 10, the AC power is secured by the three-phase uninterruptible power supply 20, and the operation of the matrix converter 30 can be continued.
[0007]
Here, the configuration and operation of the matrix converter are described in Non-Patent Document 1 below. Non-interruptible power supply systems are described in Non-Patent Document 2.
[0008]
[Non-patent document 1]
The Institute of Electrical Engineers of Japan, Special Committee on Investigation of Semiconductor Power Conversion Systems, “Power Electronics Circuit”, 1st edition, published by Ohmsha, November 30, 2000, p. 219-p. 223
[Non-patent document 2]
The Institute of Electrical Engineers of Japan, Special Committee on Investigation of Semiconductor Power Conversion Systems, “Power Electronics Circuit”, 1st edition, published by Ohmsha, November 30, 2000, p. 232 to p. 235
[0009]
[Problems to be solved by the invention]
As described above, installing the three-phase uninterruptible power supply 20 as a countermeasure in the event of a power failure not only makes the system expensive, but also increases the size of the entire system. Further, when a factor other than the power supply abnormality, for example, an abnormal situation such as an open failure occurs in the semiconductor switches 31 to 39, the operation must be stopped, and the operation cannot be continued.
[0010]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an inexpensive and compact backup device that enables continuation of operation even when a power supply abnormality occurs or a failure occurs in a semiconductor switch of a matrix converter.
[0011]
[Means for Solving the Problems]
In order to solve the above problem, the invention according to claim 1 includes a matrix converter that converts a polyphase AC voltage into a polyphase AC voltage by using a virtual rectifier and a virtual inverter, wherein a control pulse of the virtual rectifier and a control of the virtual inverter are provided. In an AC-AC power converter that synthesizes a pulse and gives the matrix converter with the pulse,
Abnormality detecting means for detecting an abnormality of the polyphase AC voltage supplied to the virtual rectifier; and, when an abnormality is detected by the abnormality detecting means, a DC voltage is used instead of the polyphase AC voltage supplied to the virtual rectifier. To the input side of the virtual rectifier, and means for turning on a predetermined semiconductor switch in the matrix converter and turning off other semiconductor switches so that the DC voltage appears in the virtual DC link section of the matrix converter. And with.
[0012]
The invention according to claim 2 is a matrix converter that converts a polyphase AC voltage into a phase AC voltage,
A faulty switch detecting means for detecting an input phase to which a faulty semiconductor switch in the matrix converter is connected as a faulty phase; and a polyphase supplied to the matrix converter when a fault is detected by the faulty switch detecting means. Means for supplying a DC voltage between the input phase lines other than the failed phase instead of the AC voltage, and turning on and off a semiconductor switch connected to the input phase supplied with the DC voltage by the means; For turning off all the semiconductor switches connected to the switch.
[0013]
The invention according to claim 3 includes a matrix converter that converts a polyphase AC voltage into a polyphase AC voltage by using a virtual rectifier and a virtual inverter, and synthesizes a control pulse of the virtual rectifier and a control pulse of the virtual inverter to synthesize the control pulse. In an AC-AC power converter provided to a matrix converter,
Faulty switch detecting means for detecting an input phase to which the faulty semiconductor switch in the matrix converter is connected as a faulty phase, and a multi-phase circuit which is supplied to the virtual rectifier when a fault is detected by the faulty switch detecting means. Means for supplying a DC voltage between the input phase lines other than the failed phase instead of the AC voltage, and turning on and off a semiconductor switch connected to the input phase supplied with the DC voltage by the means; For turning off all the semiconductor switches connected to the switch.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 is a configuration diagram showing a first embodiment of the present invention, and corresponds to the first aspect of the present invention. In FIG. 1, the same components as those in FIG. 4 are denoted by the same reference numerals, and the description below will focus on those parts that differ from FIG. 4.
[0015]
In FIG. 1, reference numeral 80 denotes a changeover switch connected between the three-phase AC power supply 10 and the matrix converter 30, and includes a switch 81 provided for the R phase and a switch 82 provided for the T phase. .
The switch 81 has an R-phase terminal e of the matrix converter 30 and R-phase and S-phase terminals a and b of the power supply 10. A DC power supply is connected between the terminal b and the S-phase of the power supply 10. 83 are connected. The switch 82 includes a T-phase terminal f of the matrix converter 30 and S-phase and T-phase terminals c and d of the power supply 10. These switches 81 and 82 are switched in response to an abnormality detection signal from a power supply abnormality detection means 70 described later. When the three-phase AC power supply 10 is normal, the terminals a and e and the terminals d and f are connected to each other, and a three-phase AC voltage from the power supply 10 is input to the matrix converter 30.
[0016]
Further, a power supply abnormality detecting means 70 is connected to a three-phase output terminal of the power supply 10 to output an abnormality detection signal for switching the changeover switch 80 when the power supply is abnormal, In order to turn on the semiconductor switch, a switch-on command is output to the rectifier control means 40.
[0017]
Next, the operation of this embodiment will be described.
When a power failure, a voltage drop, a significant voltage imbalance, or the like of the three-phase AC power supply 10 occurs and an abnormality occurs in the three-phase AC voltage supplied to the matrix converter 30, the power supply abnormality detection means 70 detects these abnormalities. Then, an abnormality detection signal is output to the changeover switch 80. As a result, the switches 81 and 82 are switched, and the terminals b and e and the terminals c and f are connected to each other.
[0018]
By the above switch operation, the input power of the matrix converter 30 is switched from the three-phase AC power supply 10 to the DC power supply 83, and a DC voltage is input to the matrix converter 30. Therefore, the operation of the virtual rectifier for converting the three-phase alternating current to direct current is not required, and the voltage of the direct current power source 83 is applied to the virtual direct current link by turning on only the semiconductor switch to which the direct current power source 83 is connected on the virtual rectifier side. To appear.
In the example of FIG. 1, the DC power supply 83 is connected between the R-phase and S-phase lines when the power supply is abnormal, so that the virtual switch S _RP of the upper arm and the virtual switch S _SN of the lower arm in FIG. 5 are turned on. If the other switches are turned off, the voltage of the virtual DC link unit becomes equal to the voltage of the DC power supply 83. Therefore, the power supply abnormality detecting means 70 in FIG. 1 uses the switches for turning on the virtual switches S _RP and S _SN. An on command is output to the rectifier control means 40.
[0019]
At this time, the virtual inverter in the matrix converter 30 may perform a normal DC-AC conversion operation as in the case where the virtual rectifier is operating.
As a result, even if an abnormality occurs in the three-phase AC power supply 10 (three-phase AC voltage), the operation of the power converter can be continued without changing the magnitude or phase of the output voltage of the matrix converter 30. In particular, in the present embodiment, it is not necessary to use the three-phase uninterruptible power supply 20 unlike the prior art of FIG. 4, and the power supply abnormality detecting means 70, the changeover switch 80, the DC power supply 83, etc. are relatively inexpensive and small. In addition, the cost and size of the device can be reduced.
[0020]
In this embodiment, the DC power supply 83 is connected between the R and S phase lines by the changeover switch 80 when the power supply abnormality is detected. However, the DC power supply 83 may be connected between other lines. Further, instead of using a single DC power supply, the DC power supply may be connected between the R, S phase and S, T phase lines.
[0021]
Next, a second embodiment of the present invention will be described with reference to FIGS. The second embodiment corresponds to the second and third aspects of the invention.
In the present embodiment, as shown in FIG. 2, the failure switch detection means 100 connected to the matrix converter 30 connects the failure detection signal indicating that the semiconductor switch constituting the matrix converter 30 has failed to the failed semiconductor switch. When the failure is detected, the three-phase AC power supply 10 is disconnected from the input side of the matrix converter 30, and the connection phase switching selecting means 94 is used to output a signal between the input phase lines other than the failed phase. A DC power supply 95 is connected, and only semiconductor switches connected to these input phases are turned on / off.
[0022]
2, contacts 91, 92, and 93 are connected to each phase between the three-phase AC power supply 10 and the matrix converter 30, and these contacts 91, 92, and 93 are connected to a failure detection signal from the failure switch detection means 100. It is opened in conjunction with. Further, in the changeover switch 90, there is provided a connection phase switching selection means 94 to which a DC power supply 95 is connected, and the operation of the selection means 94 causes the DC power supply 95 to switch each phase on the input side of the matrix converter 30. Of the two phases can be selectively connected. It should be noted that the failure detection signal and the failure phase information from the failure switch detection means 100 are input to the connection phase switching selection means 94.
The connection phase switching selection means 94 outputs the input phase (connection phase) to which the DC power supply 95 is connected to the rectifier control means 40 as connection phase information.
[0023]
In this embodiment, an open failure is assumed as a failure of the semiconductor switches 31 to 30. In general, semiconductor switches can cause short-circuit faults, but short-circuit faults are often caused by large currents, so open-circuit faults occur as a result of connecting a fast-acting fuse in series with the switch to prevent short-circuit faults. Can be done. By taking such measures, most failures can be treated as open failures.
Further, the failure detection by the failure switch detecting means 100 is performed, for example, by comparing the on / off command of the switch with the voltage across the switch, and when the voltage across the switch is abnormally high despite the ON command being given to the switch. Can be realized by determining that a failure has occurred.
[0024]
FIG. 3 shows an operation when a switch failure occurs in the embodiment of FIG.
In the matrix converter, three output phase semiconductor switches are connected to one output phase, so even if one of the three input phases fails, the other two input phase switches can perform chopping operation. It is. Therefore, the connection phase switching selection means 94 controls the DC power supply 95 to be connected between the lines of the two input phases other than the failed phase, and as the connection phase information, the input phase to which the DC power supply 95 is connected. Is transmitted to the rectifier control means 40 to turn on / off the switch connected to the rectifier control means 40.
[0025]
For example, in FIG. 3, when the switch 33 connected to the R phase of the input phase has an open fault, the contacts 91, 92, and 93 in FIG. With the phase AC power supply 10 cut off, a DC power supply 95 is connected between the input phase S-phase and T-phase lines as shown on the right side of FIG. Further, if the other switches 31 and 32 connected to the R phase are also fixed in the off state, the switches 34 to 39 connected to the S phase and the T phase of the input phase are controlled to be on and off, so that the three phases are controlled. An AC voltage can be output.
That is, all switches connected to the same input phase (failed phase) as the switch having the open fault are fixed in the off state, and the DC power supply 95 is connected between the lines of the other two input phases (healthy phases). If the switches connected to these two input phases are on / off controlled, the matrix converter 30 can be equivalently operated as an inverter, and an AC voltage having an arbitrary magnitude and frequency can be generated.
[0026]
The matrix converter can perform only a single-phase AC conversion operation at the time of phase loss or switch failure. Since the instantaneous power of single-phase AC has a pulsation twice as large as the power supply frequency, a matrix converter without a large energy buffer cannot output constant instantaneous power. However, by connecting the DC power supply 95 to the input side and turning on and off a predetermined switch as in this embodiment, it is possible to extract a constant instantaneous power on the input side and to output a constant instantaneous power. Can be. As a result, even when a switch of a certain phase fails, the operation can be continued without lowering the control performance.
[0027]
The present invention is also applicable to the mutual conversion of polyphase alternating currents other than the three-phase described in each embodiment.
[0028]
【The invention's effect】
As described above, according to the present invention, in an AC-AC power converter that does not have a large-capacity energy buffer such as a matrix converter, a DC voltage is supplied to the input side even when a power failure or a semiconductor switch failure occurs. Then, by performing on / off control of a predetermined semiconductor switch, continuous operation can be performed. In addition, since it can be provided at a low cost with a relatively simple circuit configuration as compared with the conventional technology having an uninterruptible power supply, improvement in reliability and economy can be expected.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of the present invention.
FIG. 2 is a configuration diagram showing a second embodiment of the present invention.
FIG. 3 is an equivalent circuit diagram configured when a certain semiconductor switch fails in FIG.
FIG. 4 is a configuration diagram showing a conventional technique.
FIG. 5 is an equivalent configuration diagram of a main circuit in FIG. 4;
[Explanation of symbols]
10: three-phase AC power supply 30: matrix converters 31 to 39: semiconductor switch 40: rectifier control means 50: inverter control means 60: PWM pulse synthesis means 70: power supply abnormality detection means 80, 90: changeover switches 81, 82: switch 83 , 95: DC power supplies 91, 92, 93: contacts 94: connection phase switching selecting means 100: fault switch detecting means a to f: terminals R, S, T: AC input terminals U, V, W: AC output terminals

Claims (3)

A matrix converter for converting a polyphase AC voltage into a polyphase AC voltage by a virtual rectifier and a virtual inverter, and synthesizing a control pulse of the virtual rectifier and a control pulse of the virtual inverter to provide AC-AC power to the matrix converter In the converter,
Abnormality detecting means for detecting an abnormality of the polyphase AC voltage supplied to the virtual rectifier; and, when an abnormality is detected by the abnormality detecting means, a DC voltage is used instead of the polyphase AC voltage supplied to the virtual rectifier. To the input side of the virtual rectifier, and means for turning on a predetermined semiconductor switch in the matrix converter and turning off other semiconductor switches so that the DC voltage appears in the virtual DC link section of the matrix converter. And a backup device for an AC-AC power converter. In a matrix converter that converts a polyphase AC voltage to a phase AC voltage,
Faulty switch detection means for detecting an input phase to which a faulty semiconductor switch in the matrix converter is connected as a faulty phase,
A means for supplying a DC voltage between input phase lines other than the failed phase, instead of the polyphase AC voltage supplied to the matrix converter when a failure is detected by the failure switch detection means;
Means for turning on / off a semiconductor switch connected to an input phase supplied with a DC voltage by this means and turning off all semiconductor switches connected to the failed phase. Backup device for AC power converter. A matrix converter for converting a polyphase AC voltage into a polyphase AC voltage by a virtual rectifier and a virtual inverter, and synthesizing a control pulse of the virtual rectifier and a control pulse of the virtual inverter to provide AC-AC power to the matrix converter In the converter,
Faulty switch detection means for detecting an input phase to which a faulty semiconductor switch in the matrix converter is connected as a faulty phase,
A means for supplying a DC voltage between input phase lines other than the failed phase, instead of the multi-phase AC voltage supplied to the virtual rectifier when a failure is detected by the failure switch detection means;
Means for turning on / off a semiconductor switch connected to an input phase supplied with a DC voltage by this means and turning off all semiconductor switches connected to the failed phase. Backup device for AC power converter.

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