JP2010166654A - Uninterruptible power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an uninterruptible power supply device the efficiency of which under light load is enhanced without causing disturbance in control. <P>SOLUTION: The uninterruptible power supply device is comprised of: multiple inverter/converter modules 2A, 2B, ..., 2N in which the alternating-current outputs of inverters are connected in parallel to supply power to a load; an operation quantity selecting means 6 for selecting inverter/converter modules to be operated from among these inverter/converter modules 2A, 2B, ..., 2N; a load factor transition monitoring means 5 that monitors the temporal transition of the load factor of all the inverter/converter modules selected by the operation quantity selecting means 6 and under parallel operation. According to the temporal transition of the overall load factor, the load factor transition monitoring means 5 supplies the operation quantity selecting means 6 with the quantity of inverter/converter modules to be operated among the inverter/converter modules 2A, 2B, ..., 2N. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an uninterruptible power supply device including a plurality of inverter / converter modules, and more particularly to an uninterruptible power supply device having improved operating efficiency.

  Since the conventional uninterruptible power supply is designed on the assumption that power is always supplied to the rated load, the efficiency tends to decrease at a light load of 60% or less, for example. For this reason, in a parallel connection type uninterruptible power supply that connects multiple uninterruptible power supply units in parallel and feeds power to the load, the appropriate number of operating units in the current load is judged, and as a result, only the required number of operating units is operated (For example, refer to Patent Document 1).

JP-A-3-124228 (page 1-3, FIG. 1)

  According to the method described in Patent Document 1, attention is paid only to the current load, and the past transition of the load is not considered. For this reason, even if the load factor of the uninterruptible power supply is changing, the number of operating units is changed, and the control is disturbed. There was a case to come.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide an uninterruptible power supply device that improves efficiency at light loads without causing control disturbance.

In order to achieve the above object, an uninterruptible power supply according to the present invention includes a plurality of inverter / converter modules that are connected in parallel with each other and connected to an AC output of an inverter to supply a load;
The number of operating units selecting means for selecting an inverter / converter module to be operated from among the plurality of inverter / converter modules, and the time of the overall load factor of the inverter / converter modules selected by the operating number selecting means and operating in parallel Load factor transition monitoring means for monitoring transition, wherein the load factor transition monitoring means is an inverter / converter to be operated among the plurality of inverters / converter modules according to the time transition of the overall load factor. The number of converter modules is given to the operation number selection means.

  According to the present invention, it is possible to provide an uninterruptible power supply device that improves efficiency at light load without causing disturbance of control.

The block block diagram of the uninterruptible power supply which concerns on Example 1 of this invention. The operation flow chart of a load factor transition detector. Approximate efficiency characteristics with respect to the load factor of the inverter / converter module. The block block diagram of the uninterruptible power supply which concerns on Example 2 of this invention.

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

  Hereinafter, the uninterruptible power supply according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 3.

  FIG. 1 is a block diagram of the uninterruptible power supply according to Embodiment 1 of the present invention. The AC input voltage supplied from the AC power source 1 is supplied to N inverter / converter modules 1A, 1B,..., 1N converter units connected in parallel, and these N inverter / converter modules 1A, 1B,. .. The AC output of the 1N inverter unit is connected in parallel and supplied to the load 3. Each inverter / converter module 2 normally receives a direct current input and converts it into direct current to convert the power device into a bridge, and receives the direct current from the converter and converts it back into alternating current. In order to maintain power supply to the load 3 when the AC power source 1 has a power failure, a DC power source connected to the DC unit is provided. Is not shown. In addition, an input switch and an input filter are usually provided between the AC power source 1 and each inverter / converter module 2, and an output filter is provided between each inverter / converter module 2 and the load 3. Is also omitted.

  The load current flowing through the load 3 is detected by the current detector 4 and given to the load factor transition detector 5. Although details of the operation of the load factor transition detector 5 will be described later, a command for the number of inverter / converter modules 2 to be operated is given to the operating unit selection circuit 6 based on the monitoring result of the load factor transition. Based on the command given from the load factor transition detector 5, the number-of-operations selection circuit 6 operates the inverter / converter module to be operated for each of the N inverter / converter modules 1A, 1B,. (ON command) is output. In other words, a stop command (OFF command) is output to the inverter / converter module to be stopped.

  FIG. 2 shows an operation flowchart of the load factor transition detector 5. The load factor transition detector 5 first determines whether or not the load variation is within an allowable value (step S1). In this step S1, a difference between the current load current and a predetermined time before, for example, 30 minutes before is checked, and when there is a fluctuation exceeding plus or minus 10%, it is determined that the allowable value is exceeded.

  When the load fluctuation allowable value is exceeded in step S1, a command to operate all N inverter / converter modules is output (step S2), and the process returns to step S1. This is because, for example, a load fluctuation exceeding 10% indicates that the load state is unstable. For example, in a transient state in which a load application operation is performed to start plant operation, a relatively large load may be continuously input. For this reason, all inverter / converter modules are operated based on the concept of priority on continuous operation.

  When the load fluctuation is within an allowable value in step S1, it is determined whether or not the load factor with respect to the current number of operating inverter / converter modules is 60% or less during a predetermined period (step S3). In step S3, if the load factor is not 60% or less for a predetermined period, the process returns to step S1.

  If the load factor is 60% or less for a predetermined period in step S3, whether or not the load factor based on the reduced number of operating units becomes a desired load factor when the number of operating units is reduced from the current state. Determine (step S4). If the desired load factor cannot be obtained even if the number of operating units is reduced in step S4, the process returns to step S1.

  When the number of operating units is reduced from the current state in step S4, if the load factor based on the reduced number of operating units becomes a desired load factor, a command to reduce the number of operating units is output (step S5). ) Return to step S1.

  Next, details of the determination in step S4 will be described below with reference to FIG.

FIG. 3 shows a schematic efficiency characteristic with respect to the load factor (load current) of the inverter / converter module 2. As shown in FIG. 3, the normal inverter / converter module 2 has the maximum efficiency when the load factor is between 70% and 80%, and the efficiency decreases when the load factor is 70% or less or 80% or more. . In particular, since the decrease in efficiency becomes significant when the load factor becomes 60% or less, when the load factor becomes 60% or less in step S3, for example, in step S4, the reduction of the number of operating units is determined.

  For example, consider a case where the number N of inverter / converter modules 2 is three. At this time, if the load factor determined in step S3 is 60%, the load factor when the number of operating units is reduced is 60% × 3/2 = 90%. However, since this value does not fall within the desired range of 80% or less, the determination in step S4 is N. However, when the load factor further decreases and the load factor determined in step S3 decreases to 53%, the load factor when the number of operating units is reduced is 53% × 3/2 = 79.5%. Since it is 80% or less and falls within the desired range, the determination in step S4 is Y.

  In the above, if the number N of inverter / converter modules 2 is 4, when the load factor determined in step S3 is 60%, the load factor when one unit is reduced is 60% × 4/3 = 80. Therefore, the determination in step S4 is immediately Y, and the number of operating units is changed from four to three. If the load factor is further reduced and the load factor becomes 53% on the basis of operation of 3 units, as described above, the number of operating units should be further reduced by 1 and operation at a load factor of 79.5% on the basis of 2 units. It becomes.

  As is apparent from the above description, the load factor transition monitoring circuit 5 needs to store the number reduction command instructed by itself and always know the current number of operating inverter / converter modules 2.

  In an application where the load fluctuation is frequent, unless the setting of the permissible value in the predetermined period in step S1 is appropriately selected, the stage where the energy saving operation is performed in step S4 may not be reached. Further, when the load fluctuation is always gradual, instead of step S1, when the load factor exceeds a predetermined value, the number of operating units may be added to enter the desired load factor.

  FIG. 4 is a block diagram of the uninterruptible power supply according to Embodiment 2 of the present invention. About each part of this Example 2, the same part as each part of the block block diagram of the uninterruptible power supply apparatus which concerns on Example 1 of this invention of FIG. 1 is shown with the same code | symbol, and the description is abbreviate | omitted. The second embodiment is different from the first embodiment in that each module operation time integration circuit 7 for exchanging signals with the operation number selection circuit 6 is provided.

  When the number-of-operations selection circuit 6 receives a command to reduce the number of operations from the load factor transition monitoring circuit 5, the inverter / converter module 2 to be stopped is not mentioned in the first embodiment. Has a function of specifying the inverter / converter module 2 to be stopped. That is, each module operation time integration circuit 7 integrates the approximate operation time of each inverter / converter module 2 based on, for example, the time during which the operation number selection circuit 6 outputs an operation command for each inverter / converter module 2. Keep it.

  When the operating number selection circuit 6 receives a command to reduce the operating number from the load factor transition monitoring circuit 5, the operating number selection circuit 6 determines the approximate operating time of each inverter / converter module 2 of each module operating time integration circuit 7. With reference to the integrated data, the inverter / converter module 2 having the longest operation time is stopped. Alternatively, the inverter / converter module 2 having a shorter operation time than others is preferentially operated.

  According to the second embodiment, it is possible to equalize the operation time of each inverter / converter module, which contributes to an improvement in the operating rate of the apparatus.

  In FIG. 4, it is obvious that each module operation time integration circuit 7 may be provided inside the operation number selection circuit 6.

  Further, in place of each module operation time integration circuit 7, for energy saving operation, a circuit for storing the history of each inverter / converter module being stopped is provided so that the inverter / converter module having a small stop history is preferentially operated. The inverter / converter module to be stopped may be selected to equalize the number of operations.

1 AC power supply 2, 2 A, 2 B,..., 2 N Inverter / converter module 3 Load 4 Current detector 5 Load factor transition monitoring circuit 6 Number of operation selection circuit 7 Operation time integration circuit for each module

Claims (7)

A plurality of inverter / converter modules that connect the AC outputs of the inverters in parallel to supply power to the load;
An operation number selection means for selecting an inverter / converter module to be operated among the plurality of inverter / converter modules;
Load factor transition monitoring means for monitoring the time transition of the overall load factor of the inverter / converter modules selected by the operating unit selection means and operating in parallel;
The load factor transition monitoring means includes:
The uninterruptible power supply is characterized in that the number of inverter / converter modules to be operated among the plurality of inverter / converter modules is given to the operating number selection means according to the time transition of the overall load factor. Power supply. The load factor transition monitoring means includes:
The load factor is 60% or less continuously for a predetermined period,
And when the load factor when the number of operating units is reduced falls within the predetermined load factor range,
2. The uninterruptible power supply according to claim 1, wherein a command for reducing the number of operating units is given to the operating unit selecting means.   The uninterruptible power supply according to claim 2, wherein the range of the predetermined load factor is 70% or more and 80% or less. The load factor transition monitoring means includes:
When the fluctuation of the load factor within a predetermined period exceeds an allowable value,
The uninterruptible power supply according to any one of claims 1 to 3, wherein a command for operating all the inverter / converter modules is given to the operating number selection means.   The uninterruptible power supply according to claim 4, wherein the allowable value is plus or minus 10%. The operation number selection means is
Means for accumulating the cumulative operation time of each of the inverter / converter modules is provided, and when an inverter / converter module to be operated is selected, the inverter / converter module having a short cumulative operation time is preferentially selected for operation. The uninterruptible power supply according to any one of claims 1 to 5. The operation number selection means is
Each inverter / converter module has means for storing a history of operation stop, and when selecting an inverter / converter module to be operated, an inverter / converter module with a large number of stop history is preferentially selected for operation. The uninterruptible power supply according to any one of claims 1 to 5.

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