JP2007181331A - Inverter system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inverter system that can continue its operation with other good inverters even if an inverter fails by a DC short circuit. <P>SOLUTION: This inverter system comprises a plurality of inverter groups 4 consisting of a plurality of inverter devices 5 powered from a common DC power supply 1. It performs the degeneration operation of a load even if at least one group of a plurality of the inverter groups 4 stops its operation. In this system, DC reactors 3 are provided comprehensively at the DC input portion of each inverter group 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inverter system including a plurality of inverters connected to a common DC bus.

In an inverter system constituted by a plurality of independently operable inverters and configured to drive one or a plurality of electric motors, when one inverter fails, the failed inverter is disconnected from the inverter system, Conventionally, there have been many needs for continuously operating an inverter system (hereinafter referred to as “degenerate operation”) with a limited capacity or number of units by other healthy inverters. For this reason, a switch is provided on the input side and output side of each inverter, and the input / output switch of the inverter is opened by the failure signal of each inverter, and the inverter system is operated according to the load state before the failure. The proposal which aims at continuation is made | formed (for example, refer patent document 1).
JP-A-9-275699 (page 3, FIG. 1)

  According to the technique disclosed in Patent Document 1, a failed inverter among a plurality of inverters is disconnected from the entire inverter system, and, for example, the operation speed of the motor is reduced according to the capacity of the remaining inverters, so that the operation by degenerate operation is performed. Since the continuation is planned, the operating rate of the inverter system is greatly improved.

  However, in an inverter system in which a plurality of inverters are connected to a common DC power source, for example, when one inverter fails due to a DC short circuit, an excessive current flows from another healthy inverter to the short circuit point. Other healthy inverters also become overcurrent and stop operation, which may prevent the system from continuing operation.

  The present invention has been made in view of the above problems, and in an inverter system in which a plurality of inverters are connected to a common DC power source, even if one inverter is short-circuited by another DC, another healthy inverter An object of the present invention is to provide an inverter system that can continue operation.

  In order to achieve the above object, an inverter system according to a first invention of the present invention has a plurality of inverter groups each including a plurality of inverter devices fed from a common DC power supply, and at least of the plurality of inverter groups. In an inverter system capable of performing a degenerate operation even when one set is stopped, a DC reactor is collectively provided in each DC input unit of the inverter group.

  The inverter system according to the second aspect of the present invention includes a plurality of inverter groups each including a plurality of inverter devices fed from each of a plurality of DC power supplies, and at least one of the plurality of inverter groups. In the inverter system capable of degenerate operation of the load even when the operation is stopped, the outputs of the plurality of DC power supplies are connected to each other via DC reactors.

  According to the present invention, it is possible to provide an inverter system that can continue to operate with another healthy inverter even if one inverter has a DC short-circuit fault.

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

  Hereinafter, an inverter system according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a circuit configuration diagram of an inverter system according to Embodiment 1 of the present invention.

  The output of the DC power source 1 is connected to a DC bus 2 provided in common. A plurality of buses branch from the common bus 2 and are fed to the inverter groups 4a, 4b and 4c via the DC reactors 3a, 3b and 3c, respectively.

  The inverter group 4a is composed of a plurality of inverter devices 5a, 5b and 5c. Similarly, the inverter group 4b is composed of a plurality of inverter devices 5d, 5e and 5f, and the inverter group 4c is composed of a plurality of inverter devices 5g, 5h and 5i. The AC outputs of the inverter devices 5a, 5b, 5c, 5d, 5e, 5f, 5g, 5h, and 5i are fed to the AC motors 6a, 6b, 6c, 6d, 6e, 6f, 6g, 6h, and 6i, respectively.

  The inverter devices 5a, 5b, 5c, 5d, 5e, 5f, 5g, 5h, and 5i are input switches 7a, 7b, 7c, 7d, 7e, 7f, 7g, 7h, and 7i, respectively, that are provided at the inputs. Current detectors 8a, 8b, 8c, 8d, 8e, 8f, 8g, 8h and 8i for detecting, capacitors 9a, 9b, 9c, 9d, 9e, 9f, 9g, 9h and 9i for smoothing the voltage, and smoothing It comprises inverters 10a, 10b, 10c, 10d, 10e, 10f, 10g, 10h and 10i for converting the direct current voltage into alternating current.

  The AC motors 6a, 6b, 6c, 6d, 6e, 6f, 6g, 6h and 6i mechanically drive the common load machine 11. Here, the common load machine 11 corresponds to, for example, a table roller used in a steel rolling process.

  Here, each of the input switches 7a, 7b, 7c, 7d, 7e, 7f, 7g, 7h, and 7i is constituted by a fuse, a switching element, or a combination thereof, and has an overcurrent cutoff function.

  Hereinafter, with reference to FIG.1 and FIG.2, the operation | movement when a direct-current short-circuit accident generate | occur | produces in the S point of the inverter apparatus 5a is demonstrated. In addition, since it becomes the same operation | movement also when a DC short circuit accident occurs in inverter devices other than the inverter device 5a, description is abbreviate | omitted.

  When a short circuit accident occurs at the point S of the inverter device 5a, first, current flows out from the capacitors 9b and 9c, which are constituent elements of the other inverter devices 5b and 5c in the same inverter group 4a, toward the short circuit point S. At this time, the current detectors 8b and 8c detect the DC current flowing through the DC main circuits of the inverter devices 5b and 5c, and stop their own inverter operation by a protection operation when the preset DC overcurrent level is exceeded. The input switches 7b and 7c are shut off.

  Also, the inverter device 5a itself performs short-circuit current protection by the overcurrent protection function of the input switch 7a.

  Next, consider the inflow current from the DC power source 1 and the other inverter groups 4b and 4c when a short circuit occurs at the point S.

  When a DC short circuit occurs at the point S of the inverter device 5a, the current from the DC power source 1 and the other inverter groups 4b and 4c tends to flow into the point S, but the rise is limited by the DC reactor 3a. Note that rising of the inflow currents from the inverter groups 4b and 4c is restricted by the DC reactors 3b and 3c, respectively.

  Therefore, if the inductance values of the DC reactors 3a, 3b and 3c are appropriately selected, the DC power supply 1 and the inverter devices 5d, 5e, 5f, 5g, 5h and 5i in the inverter groups 4b and 4c reach the overcurrent level. By previously shutting off the input switch 7a, it becomes possible to continue operation of the DC power supply 1 and the inverter devices 5d, 5e, 5f, 5g, 5h and 5i in the inverter groups 4b and 4c.

  The important point in the above is that when a short circuit fault occurs in the inverter device in the inverter group 4a, the inverter devices 5a, 5b and 5c in the inverter group 4a are stopped, and the AC motors 6a, 6b and 6c are stopped. However, in the load machine 11, for example, if the operation speed is reduced, the inverter device and the AC motor are grouped so that the operation can be continued according to the needs. The same applies to the inverter groups 4b and 4c.

  In the above, it has been described that the inductance values of the DC reactors 3a, 3b and 3c are appropriately selected. However, the system configuration is such that the number and capacity of inverter devices in the same inverter group are balanced among the inverter groups. However, it is not necessary to select the same inductance value for the DC reactors 3a, 3b and 3c. For example, when the inductance of the bus connecting the DC reactor 3b and the DC reactor 3c is larger than the inductance of the other buses, the inductance value of the DC reactor 3c can be selected to be low accordingly.

  FIG. 2 is a circuit configuration diagram of an inverter system according to Embodiment 2 of the present invention. About each part of this Example 2, the same part as each part of the inverter system which concerns on Example 1 of FIG. 1 is shown with the same code | symbol, and the description is abbreviate | omitted. The difference between the second embodiment and the first embodiment is that the inverter group 4c is omitted and the inverter groups 4a and 4b are divided into two groups. The AC motors 12a, 12b, and 12c serving as loads are multiphase motors, and each of the AC motors. The primary winding of the predetermined phase is fed from the inverter device in the inverter group 4a, and the primary winding of the remaining phase is fed from the inverter device in the inverter group 4b.

  Here again, consider the case where a DC short-circuit accident occurs at the point S of the inverter device 5a. As described in the first embodiment, the inverter devices 5a, 5b, and 5c belonging to the same inverter group 4a as the inverter device in which the short circuit accident has occurred are stopped due to the overcurrent caused by the input switches 7a, 7b, and 7c being opened. The devices 5d, 5e and 5f will not be shut down because the current is reduced by opening the input switch 7a before reaching the overcurrent level. Therefore, among the input phases of the multiphase motors 12a, 12b and 12c, the power supply is stopped for the phases corresponding to the inverter devices 5a, 5b and 5c, but the other phases are healthy, so the output of the motor is halved, for example. If reduced, the multi-phase motors 12a, 12b and 12c can continue to operate by degenerate operation.

  FIG. 3 is a circuit configuration diagram of an inverter system according to Embodiment 3 of the present invention. Regarding the respective parts of the third embodiment, the same parts as those of the inverter system according to the second embodiment of FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted. The third embodiment is different from the second embodiment in that the outputs of the inverters 10a, 10b, 10c, 10d, 10e, and 10f are single-phase, and the output transformers 13a, 13b, and 13c use the inverter group 4a and the inverter group 4b described above. This is the point that the three-phase AC motor 6 is driven by combining the single-phase outputs.

  The above configuration is a so-called serial multiplex system in which each phase of the primary winding of the three-phase AC motor 6 is combined in series with the single-phase output of the inverter in the inverter group 4a and the single-phase output of the inverter in the inverter group 4b. It is.

  Here again, consider the case where a DC short-circuit accident occurs at the point S of the inverter device 5a. As described in the first embodiment and the second embodiment, the inverter devices 5a, 5b, and 5c belonging to the same inverter group 4a as the inverter device in which the short circuit accident has occurred are stopped due to the input switches 7a, 7b, and 7c being opened due to overcurrent. However, the inverter devices 5d, 5e, and 5f do not stop operating. Therefore, for example, the drive voltage can be reduced by half and the AC motor 6 can be continuously operated by the degenerate operation.

  FIG. 4 is a circuit configuration diagram of an inverter system according to Embodiment 4 of the present invention. Regarding the respective parts of the fourth embodiment, the same parts as those of the inverter system according to the first embodiment of FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. The fourth embodiment is different from the first embodiment in that two DC power sources, ie, a DC power source 1a and a DC power source 1b, are provided, and one DC reactor 3 is provided between the common bus 2 connecting the DC power source 1a and the DC power source 1b. In addition, the inverter group 4c is omitted and the inverter groups 4a and 4b are configured in two groups. In addition, illustration of the load machine 11 is abbreviate | omitted in FIG.

  The fourth embodiment is applicable when there are a plurality of DC power supplies. Multiple DC power supplies are used in order to compensate for the current capacity when one DC power supply is insufficient, or when one DC power supply stops due to a failure, another DC power supply uses an inverter. This is to continue the operation of the system.

  As shown in FIG. 4, the DC reactor 3 is inserted into the common bus 2 that connects the inverter group 4a and the inverter group 4b.

  Here again, consider the case where a DC short-circuit accident occurs at the point S of the inverter device 5a. As described in the first to third embodiments, the inverter devices 5a, 5b, and 5c belonging to the same inverter group 4a as the inverter device in which the short circuit accident has occurred are stopped due to the input switches 7a, 7b, and 7c being opened due to overcurrent. To do. On the other hand, the inverter devices 5d, 5e, and 5f do not stop operation because the current decreases due to the opening of the input switch 7a before reaching the overcurrent level.

  Here, it is considered that there is no DC reactor for limiting the short-circuit current from the DC power supply 1a to the short-circuit point S. However, the DC power supply 1a normally has a large overcurrent capability, and the rise of this short-circuit current is This is not a problem because it is much slower than the rise of the inflow current from other inverter devices in the same group.

  As described above, in an inverter system having a plurality of DC power supplies, an inverter group is connected to each DC power supply, and a DC reactor having an appropriate reactance is connected to a DC bus connecting each DC power supply. The inverter devices belonging to the inverter group that has caused the DC short circuit are stopped, but the inverter devices belonging to other inverter groups can be continuously operated.

  Also, if the load ratio is equal among the inverter groups, current is supplied from each DC power source to the inverter group connected to the DC power source, and the DC reactor installed in the middle has almost no current during normal operation. Therefore, a DC reactor having a small current capacity can be applied.

  In the first to fourth embodiments described above, the number of inverter groups and the number of inverter devices belonging to each inverter group are limited to two to three. However, these may be any number of two or more. it is obvious.

The circuit block diagram of the inverter system which concerns on Example 1 of this invention. The circuit block diagram of the inverter system which concerns on Example 2 of this invention. The circuit block diagram of the inverter system which concerns on Example 3 of this invention. The circuit block diagram of the inverter system which concerns on Example 4 of this invention.

Explanation of symbols

1, 1a, 1b DC power supply 2 DC bus 3, 3a, 3b, 3c DC reactor 4a, 4b, 4c Inverter groups 5a, 5b, 5c, 5d, 5e, 5f, 5g, 5h, 5i Inverter devices 6, 6a, 6b 6c, 6d, 6e, 6f, 6g, 6h, 6i AC motors 7a, 7b, 7c, 7d, 7e, 7f, 7g, 7h, 7i Input switches 8a, 8b, 8c, 8d, 8e, 8f, 8g, 8h 8i Current detectors 9a, 9b, 9c, 9d, 9e, 9f, 9g, 9h, 9i Capacitors 10a, 10b, 10c, 10d, 10e, 10f, 10g, 10h, 10i Inverter 11 Load machine 12a, 12b, 12c Phase motor 13a, 13b, 13c Output transformer

Claims (6)

Having multiple inverter groups consisting of multiple inverter devices fed from a common DC power supply,
An inverter system capable of degenerate operation of a load even when at least one of the plurality of inverter groups stops operation,
An inverter system characterized in that a DC reactor is collectively provided in each DC input section of the inverter group. Having a plurality of inverter groups consisting of a plurality of inverter devices fed from each of a plurality of DC power supplies,
An inverter system capable of degenerate operation of a load even when at least one of the plurality of inverter groups stops operation,
An inverter system characterized in that the outputs of the plurality of DC power supplies are connected to each other via DC reactors. The DC reactor is
When one of the inverter devices has a DC short circuit,
In the time until the input switches of all inverter devices of the inverter group to which the inverter device belongs are turned off,
The inverter system according to claim 1 or 2, wherein an inductance value is selected so that an inverter device belonging to all other inverter groups does not become an overcurrent. The DC reactor is
The inverter system according to claim 3, wherein an inductance value is selected in consideration of an inductance value of a bus for supplying power to each inverter group from the DC power supply. The load is a multiphase motor;
3. The inverter according to claim 1, wherein the primary winding of each phase of the multiphase motor is configured to be supplied with power from the inverter devices of at least two different sets of the inverter groups. system. The load is an AC motor through an output transformer for series multiplexing,
3. The inverter system according to claim 1, wherein the input of each phase of the output transformer is configured to be supplied with power from the inverter devices of at least two different sets of the inverter groups.

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