| 摘要 |
PROBLEM TO BE SOLVED: To control an uninterruptible power supply in such a way as to secure the parallel redundancy and optimize the efficiency of a system.SOLUTION: A load rate monitoring unit 5 calculates a system load rate from the detected current of a current detector 4 and, when there is a fluctuation in the system load rate, calculates the load rate of each uninterruptible power supply from the system load rate. When a load rate is increasing, in which case if the load rate is 40% or less, for example, the load rate monitoring unit 5 determines the number of units n of uninterruptible power supplies which can be stopped. The number of stopped units n means the number of units which can be operated in parallel redundant mode when the load rate of each uninterruptible power supply does not exceed 90% and one of the uninterruptible power supplies is paralleled off by a fault. When the uninterruptible power supplies cannot be operated in parallel redundant mode while the load rate of each uninterruptible power supply is not increasing, the load rate monitoring unit 5 calculates the number of units m which can be put into operation in parallel redundant mode. A number of operating units selection unit 6 causes one or more of the uninterruptible power supplies to run or stop on the basis of the calculation result of the load rate monitoring unit 5. |
