JP4868575B2 - Power converter - Google Patents

Description

  The present invention relates to a power converter that drives a common AC motor by driving a plurality of unit inverters in parallel.

  In a power conversion device using multiple unit inverters, when one unit inverter fails for some reason, this failed unit inverter is disconnected and the power conversion device continues to operate using another healthy unit inverter. There are many needs to be addressed (see, for example, Patent Document 1).

  Normally, a fuse provided in a DC circuit is used as protection when a unit inverter causes a DC short circuit. That is, the unit inverter in which the DC short-circuit has occurred fuses the fuse by the short-circuit current and is disconnected from the device, thereby preventing the damage from spreading.

At this time, in order to continue operation as a power conversion device, it is necessary to detect this blown fuse. However, a microswitch is provided in the fuse, and when the fuse is blown, the microswitch is operated so that the fuse It was normal to detect fusing.
JP 2003-333862 A (page 3-4, FIG. 1)

  The power conversion device disclosed in Patent Document 1 is a so-called serial multiplex system in which the output of a unit inverter is synthesized by a secondary winding of a transformer provided in common on the output side to output a high voltage. However, even if the unit inverter is connected in parallel to drive the AC motor, which is a common load, there is a great need for continued operation as the power converter described above.

  In addition, the above-described detection method for detecting a blown fuse using a microswitch may not only cause a malfunction of the microswitch, but also causes an insulation problem when the voltage of the unit inverter is high, resulting in a large unit inverter. There was a problem.

  The present invention has been made in view of the above, and provides a unit inverter parallel drive power converter capable of reliably detecting a fuse blow of a unit inverter and continuing operation with another healthy unit inverter. For the purpose.

To achieve the above object, power conversion apparatus of the present invention has the following features.

A power conversion device according to a first aspect of the present invention includes a rectifier circuit that converts an AC voltage supplied from an AC power source into a DC voltage, a DC capacitor that smoothes the DC voltage, and the smoothed DC voltage that is converted into an AC voltage. A power converter that drives a common AC motor by connecting a plurality of unit inverters composed of an inverter circuit for converting to a voltage and a fuse provided to protect against a short-circuit failure of the inverter circuit in parallel. When the output current during operation of the unit inverter increases to a predetermined value or more, all the unit inverters are once gate-blocked, and when the gate block is released and restarted, the output current is If the ripple of the double component of the increased operating frequency of the output current of the unit inverter exceeds a predetermined value, all the unit inverters are gated again. Lock, after a predetermined time, separated from the driving system by means disconnects the unit inverters is characterized in that so as to restart by releasing the gate blocks of another unit inverter except the unit inverter.

A power converter according to a second aspect of the present invention includes a rectifier circuit that converts an AC voltage supplied from an AC power source into a DC voltage, a DC capacitor that smoothes the DC voltage, and the smoothed DC voltage. A power converter that drives a common AC motor by connecting a plurality of unit inverters in parallel, each of which is composed of an inverter circuit that converts AC to AC voltage and a fuse provided to protect against a short-circuit failure of the inverter circuit The control unit that supplies the gate pulse of each unit inverter has a double configuration, and when the DC voltage during operation of any one of the unit inverters decreases to a predetermined value or less, all the unit inverters After a predetermined time, at least one of the input current and output current of the unit inverter whose DC voltage has decreased reaches a predetermined level. When the unit inverter is disconnected from the drive system by the disconnecting means, the gate blocks of other unit inverters other than the unit inverter are released and restarted, and after the predetermined time, the DC voltage has decreased. When at least one of the input current and output current of the inverter does not reach a predetermined level, the control unit configured to be duplicated is switched from one to the other, and the gate blocks of all unit inverters are released and restarted. It is characterized by that.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the unit inverter parallel drive power converter device which can detect the fuse blow of a unit inverter reliably and can continue an operation | movement with another healthy unit inverter.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a circuit configuration diagram of a power conversion apparatus according to Embodiment 1 of the present invention. In FIG. 1, rectifier circuits 1a and 1b convert AC voltage supplied from an AC power source through input switches 7a and 7b, respectively, into DC voltage. This DC voltage is smoothed by DC capacitors 2a and 2b, respectively, and converted to an AC voltage of an arbitrary frequency by inverter circuits 3a and 3b. Fuses 4a and 4b are provided in the DC link portions of the DC capacitors 2a and 2b and the inverter circuits 3a and 3b, respectively. The inverter circuits 3a and 3b are supplied with variable frequency AC power to the common AC motor 9 via the coupling reactors 5a and 5b and the output switches 6a and 6b, respectively, and are driven at a variable speed. In the above, the coupling reactors 5a and 5b may be transformers that increase or decrease the output voltage. For example, when the common AC motor 9 is a multi-winding motor and each unit inverter supplies power to each winding, the coupling reactors 5a and 5b can be omitted.

  In the above configuration, the rectifier circuit 1a, the DC capacitor 2a, the inverter circuit 3a, and the fuse 4a constitute a unit inverter a. Similarly, the rectifier circuit 1b, the DC capacitor 2b, the inverter circuit 3b, and the fuse 4b constitute a unit inverter b.

  Each of the inverter circuits 3a and 3b includes a plurality of conversion arms that are bridge-connected, and each conversion arm includes one or a plurality of switching elements. These switching elements are given a gate pulse from a control unit 30 described later.

  The voltage across the DC capacitors 2a and 2b is detected by the voltage detectors 8a and 8b, respectively, and is supplied to one input of the comparators 21a and 21b as the DC voltage a and DC voltage b, respectively. When the DC voltage drop detection level signal is given to the other input of the comparators 21a and 21b and the unit inverters a and b are operated, the DC voltage a and the DC voltage b fall below the DC voltage drop detection level. 1 is output to latch circuits 22a and 22b, respectively. The outputs of the latch circuits 22a and 22b are given to the time delay circuits 23a and 23b, respectively, and the input switch 7a and the output switch 6a, and the input switch 7b and the output switch 6b are output by the outputs of the time delay circuits 23a and 23b, respectively. Is configured to open.

  Note that both the input switch 7a and the output switch 6a are provided to ensure the circuit breakage, but either one may be omitted in consideration of the function of the fuse 4a.

  The configuration of the control unit 30 will be described below. In FIG. 1, the control unit 30 is a common control unit that controls the unit inverter a and the unit inverter b. However, a control unit may be provided separately for each unit inverter.

  A speed command given from the outside is given to the speed control circuit 31. The speed control circuit 31 outputs a voltage reference corresponding to the speed command, and gives this voltage reference to the gate generation circuit 32. The gate generation circuit 32 supplies a gate pulse to the switching elements of the conversion arms of the inverter circuits 3a and 3b so that a voltage that meets the voltage reference is output from the inverter circuits 3a and 3b. Here, the speed control circuit 31 may perform speed feedback control of the AC motor 9, but is not shown here. Similarly, the current control unit as a minor loop is not shown.

  The voltage drop a signal and the voltage drop b signal obtained from the latch circuits 22 a and 22 b are applied to the protection circuit 33. When any of the voltage drop signals is given, the protection circuit 33 outputs a gate block signal for stopping the gates given to all the unit inverters. The protection circuit 33 is supplied with the signals of the auxiliary contacts 24a and 24b of the output switches 6a and 6b as the output switch signal a and the output switch signal b, respectively, and when any of the output switches is opened. Then, the gate blocks of all inverter circuits except the inverter circuit that has been opened are released, and the unit inverter is restarted.

  According to the above circuit configuration, a DC short-circuit of any unit inverter is detected by a drop in DC voltage, and all inverters are gate-blocked by this voltage drop signal, and input / output of the unit inverter short-circuited after a predetermined time. It is possible to open the switch, confirm the opening of the output switch, release the gate blocks of all unit inverters other than the unit inverter, and restart the unit.

  At the time of DC short-circuiting, the DC voltage suddenly drops due to the discharge of the DC capacitor at the short-circuit point, but after the fuse is blown, the DC capacitor is charged from the rectifier circuit and the DC voltage is restored again. Since the fuse blows because the short-circuit current flows, it is possible in principle to reliably detect the DC short circuit earlier than the fuse blows if this drop in the DC voltage is detected.

  In the above description, the unit inverter has been described as having two units of the unit inverter a and the unit inverter b. However, it is obvious that the unit inverter may have three or more units.

  FIG. 2 is a circuit configuration diagram of the power conversion apparatus according to the second embodiment of the present invention. In the second embodiment, the same parts as those in the circuit configuration diagram of the power conversion apparatus according to the first embodiment of the present invention shown in FIG. The second embodiment is different from the first embodiment in that arm fuses 10a and 10b are provided in the respective conversion arms in the inverter circuits 3a and 3b in place of the fuses 4a and 4b provided in the DC link portion.

  As in the case of the first embodiment, for example, when a DC short circuit occurs in the inverter circuit 3a, the DC voltage is lowered and any arm fuse 10a in the inverter circuit is blown.

  Therefore, even when an arm fuse is provided in each conversion arm instead of the fuse 4a, the operation can be continued by restarting using a sound unit inverter in the same manner as in the first embodiment. It becomes possible.

  FIG. 3 is a circuit configuration diagram of the power conversion apparatus according to the third embodiment of the present invention. In the third embodiment, the same parts as those in the circuit configuration diagram of the power conversion apparatus according to the second embodiment of the present invention shown in FIG. The third embodiment differs from the second embodiment in that output current detectors 11a and 11b are provided instead of the voltage detectors 8a and 8b, and output current detection is performed by the comparators 34a and 34b provided in the control unit 30A. The output current a and the output current b obtained from the devices 11a and 11b are respectively compared with the output overcurrent detection level, and the output overcurrent signal is supplied to the protection circuit 33. The output current a and the output current b is input to each of the ripple detection circuits 25a and 25b, and when the current ripple is equal to or greater than a predetermined value, 1 is output and applied to the latch circuits 22a and 22b. It is the point which was comprised so that it might give to the protection circuit 33 as.

  As in the case of the second embodiment, for example, when a short circuit occurs in the inverter circuit 3a, a short circuit current flows from the DC capacitor 2a and the DC voltage decreases. Here, when the DC voltage decreases, a charging current flows from the AC motor 9 to the DC capacitor 2a. This may be considered to continue until the arm fuse 10a is blown.

  At this time, the output current a which is the output of the output current detector 11a and the output overcurrent detection level are compared by the comparator 34a to detect the output overcurrent. When the output overcurrent is detected, the protection circuit 33 gate-blocks the inverter circuits 3a and 3b. After the gate block is implemented, it is restarted once. At this time, since the arm fuse 10a is blown, the output current 29a has a ripple twice the operating frequency. A ripple current twice the operating frequency is detected by the ripple detection circuit 30a and output to the protection circuit 33 to block the inverter circuits 3a and 3b. Further, the input switch 7a and the output switch 6a are opened at a timing delayed by a predetermined time after the gate block by the time delay circuit 23a. After opening the output switch 6a, the output switching signal a from the auxiliary contact 27a is input to the protection circuit 33, and it is confirmed that the output switch 6a has been opened and restarted to continue the operation.

  According to this embodiment, the fusing of the arm fuse is reconfirmed by detecting the ripple current twice as high as the operating frequency, so that the fusing of the arm fuse can be detected more reliably.

  FIG. 4 is a circuit configuration diagram of the power conversion apparatus according to the third embodiment of the present invention. In each part of the fourth embodiment, the same parts as those in the circuit configuration diagram of the power conversion apparatus according to the third embodiment of the present invention shown in FIG. The fourth embodiment is different from the third embodiment in that a load state determination circuit 35 that receives the output currents a and b in the control unit 30B and a restart permission circuit 36 that receives the output of the load state determination circuit 35 as inputs. And the output of the restart permitting circuit 36 is given to the protection circuit 33 as an interlock condition for releasing the gate block.

  In the first to third embodiments, the example in which the unit inverter that caused the DC short-circuit is disconnected and restarted using another healthy unit inverter has been described, but the negative load state of the common AC motor 9 is confirmed. If this is not done, there is a risk of overloading at restart. Therefore, in the fourth embodiment, the load state determination circuit 35 and the restart permission circuit 36 automatically detect that no overload occurs at the time of restart.

  Since the load state determination circuit 35 needs to detect the load state of the AC motor 9 before DC short-circuit occurs in one unit inverter, it is preferable to provide a delay element inside. Further, the restart permission circuit 36 may set, for example, the entire inverter capacity when one unit inverter is disconnected in advance, and compare this set value with the detected value of the load state.

  In this embodiment, the load state of the AC motor 9 is detected by the total value of the output currents of the unit inverters. However, the AC motor is determined from other information such as input current, input or output power, motor speed, etc. Nine load states may be detected.

  Further, although the present embodiment is a unit inverter using an arm fuse, it is obvious that a unit inverter using a fuse for a DC link may be used as shown in the first embodiment.

  FIG. 5 is a circuit configuration diagram of a power conversion device according to Embodiment 5 of the present invention. In each part of the fifth embodiment, the same parts as those in the circuit configuration diagram of the power conversion apparatus according to the first embodiment of the present invention shown in FIG. The fifth embodiment is different from the first embodiment in that output current detectors 11a and 11b are provided, thereby detecting the output currents of the inverter circuits 3a and 3b, respectively, and a comparator 37a provided in the control unit 30C. A point where one input of 37b is used, an output overcurrent detection level is given to the other input of the comparators 37a and 37b, and an output of the comparators 37a and 37b is given to the switching circuit 38; The speed control circuit, the protection circuit, and the gate generation circuit in 30C are duplexed with the speed control circuits 31a and 31b, the protection circuits 33a and 33b, and the gate generation circuits 32a and 32b, and the outputs of the gate generation circuits 32a and 32b are switched. And the output of the time delay circuits 23a and 23b is connected to the AND circuits 26a and 26b. The output of the switching circuit 38 is applied to the other of the AND circuits 26a and 26b, and the output switches 6a and 6b and the input switches 7a and 7b are provided by the outputs of the AND circuits 26a and 26b. It is the point which constituted so that each might be opened.

  As described above, for example, when the fuse 4a is blown by a DC short circuit in the inverter circuit 3a, the voltage detector 8a detects a voltage drop, but current flows backward from the output side of the inverter circuit 3a. Therefore, if this current backflow is not detected, it is considered that a DC short circuit has not actually occurred and some abnormality of the control unit has occurred.

  According to the present embodiment, the comparator 37a or 37b outputs 1 when the output current of the unit inverter a or the unit inverter b is equal to or higher than the overcurrent detection level, and the switching circuit 38 outputs to the AND circuits 26a and 26b. 1 is output. The operation in this case is exactly the same as in the first embodiment. If the output current of the unit inverter a or the unit inverter b is equal to or lower than the output overcurrent detection level, it is determined that the control unit is abnormal, and the switching circuit 38 outputs 0 to invert the switch 39. Switch the control unit. In this case, the output switches 6a and 6b and the input switches 7a and 7b are not opened and the gate blocks of all unit inverters are released and restarted.

  As described above, according to this embodiment, when a voltage drop due to an abnormality of the control unit occurs, it is possible to continue operation by switching the control unit to the standby system.

  FIG. 6 is a circuit configuration diagram of a power conversion apparatus according to Embodiment 6 of the present invention. About each part of this Example 6, the same part as each part of the circuit block diagram of the power converter device which concerns on Example 5 of this invention of FIG. 5 is shown with the same code | symbol, and the description is abbreviate | omitted. The sixth embodiment differs from the fifth embodiment in that input current detectors 12a and 12b are provided instead of the output current detectors 11a and 11b, and the input current a and the input current b, which are detected values, are respectively compared with the comparator 37a. , 37b, and the other input is compared with the input overcurrent detection level.

  As described above, when a DC short circuit occurs, the DC voltage decreases. At this time, if a DC short circuit actually occurs, current flows from the input side of the unit inverter. Accordingly, as in the case of the fifth embodiment, when a voltage drop due to an abnormality of the control unit occurs, it is possible to continue operation by switching the control unit to the standby system.

  In the fifth and sixth embodiments, a DC voltage drop may be detected due to a malfunction of the voltage detection circuit 8a or the voltage detection circuit 8b. In this case, the control unit including the voltage detection circuit is duplicated, and when the input or output overcurrent does not occur, the control unit including the voltage detection circuit may be switched.

  Further, the fifth embodiment and the sixth embodiment may be used together to detect the overcurrent of both the output current and the input current, and to confirm the blowout of the DC link fuse or the arm fuse more reliably.

The circuit block diagram of the power converter device which concerns on Example 1 of this invention. The circuit block diagram of the power converter device which concerns on Example 2 of this invention. The circuit block diagram of the power converter device which concerns on Example 3 of this invention. The circuit block diagram of the power converter device which concerns on Example 4 of this invention. The circuit block diagram of the power converter device which concerns on Example 5 of this invention. The circuit block diagram of the power converter device which concerns on Example 6 of this invention.

Explanation of symbols

1a, 1b Rectifier circuit 2a, 2b DC capacitor 3a, 3b Inverter circuit 4a, 4b Fuse 5a, 5b Coupling reactor 6a, 6b Output switch 7a, 7b Input switch 8a, 8b DC voltage detection circuit 9 Three-phase AC motor 10a, 10b arm fuses 11a, 11b output current detection circuits 12a, 12b input current detection circuits 21a, 21b comparators 22a, 22b latch circuits 23a, 23b time delay circuits 24a, 24b auxiliary contacts 25a, 25b ripple detection circuits 26a, 26b AND circuit 30 , 30A, 30B, 30C Control unit 31, 31a, 31b Speed control circuit 32, 32a, 32b Gate generation circuit 33, 33a, 33b Protection circuit 35 Load state determination circuit 36 Restart permission circuit 37a, 37b Comparator 38 Switching circuit 39 Selector

Claims (8)

A rectifier circuit that converts an AC voltage supplied from an AC power source into a DC voltage;
A DC capacitor for smoothing the DC voltage;
An inverter circuit for converting the smoothed DC voltage into an AC voltage;
A fuse provided to protect against short-circuit faults in this inverter circuit
A plurality of unit inverters connected in parallel to drive a common AC motor,
When the output current during operation of any of the unit inverters increases to a predetermined value or more,
Once all the unit inverters are gate-blocked,
When the gate block is released and restarted, if the ripple of the double component of the operating frequency of the output current of the unit inverter in which the output current has increased is greater than or equal to a predetermined value,
All the unit inverters are gate-blocked again,
After a predetermined time, the unit inverter is disconnected from the drive system by the disconnecting means,
A power conversion device, wherein a gate block of other unit inverters other than the unit inverter is released and restarted. A rectifier circuit that converts an AC voltage supplied from an AC power source into a DC voltage;
A DC capacitor for smoothing the DC voltage;
An inverter circuit for converting the smoothed DC voltage into an AC voltage;
A fuse provided to protect against short-circuit faults in this inverter circuit
A plurality of unit inverters connected in parallel to drive a common AC motor,
The control unit for supplying the gate pulse of each unit inverter has a double configuration,
When the DC voltage during operation of any one of the unit inverters falls below a predetermined value,
Gate block all the unit inverters,
When at least one of the input current and output current of the unit inverter whose DC voltage has decreased after a predetermined time has reached a predetermined level,
Disconnect the unit inverter from the drive system by disconnecting means,
Release the gate block of other unit inverters except the unit inverter and restart it.
When at least one of the input current and the output current of the unit inverter whose DC voltage has decreased after the predetermined time does not reach a predetermined level,
2. The power conversion device according to claim 1, wherein the control unit configured to be duplicated is switched from one to the other, and the gate blocks of all unit inverters are released and restarted. The power converter according to claim 1, wherein the fuse is provided in each conversion arm of the inverter circuit of the unit inverter. The power converter according to claim 2, wherein the fuse is provided in an input unit of an inverter circuit of the unit inverter. Means for detecting a load state during operation of the common AC motor;
2. The power conversion device according to claim 1, wherein the restart interlock condition is that when one of the unit inverters is disconnected, the total capacity of the remaining unit inverters exceeds the load state. . Means for detecting a load state during operation of the common AC motor;
An interlock that releases and restarts the gate blocks of other unit inverters other than the unit inverter when the total capacity of the remaining unit inverters exceeds the load state when one of the unit inverters is disconnected The power converter according to claim 2, wherein the condition is set. The said separating means is at least one of the switch provided in the input side of the said unit inverter, and the switch provided in the output side, The one of the Claims 1 thru | or 6 characterized by the above-mentioned. Power conversion device. The power converter according to any one of claims 1 to 7, wherein a coupling reactor or a transformer is provided on an output side of each of the unit inverters.

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