Uninterruptible power supply
An uninterruptible power supply includes a main uninterruptible power supply unit including a converter, an inverter, and a battery, as well as an input transformer which is arranged between an AC power supply and the converter and transforms the AC voltage from the AC power supply. The uninterruptible power supply further includes a DC component extraction unit that extracts a DC component from current flowing between the AC power supply and the converter, as well as a CPU which, when the DC component extracted by the DC component extraction unit is greater than a threshold current, stops operation of the converter and causes DC voltage from the battery to be supplied to the inverter.
1. An uninterruptible power supply, comprising:
an input transformer connected to an input node that is configured to be connected to an AC power supply so as to transform AC voltage from the AC power supply;
a converter receiving the transformed AC voltage to convert the transformed AC voltage to DC voltage;
an inverter that converts the DC voltage from the converter to AC voltage for supplying to a load;
a DC power supply that is connected between the converter and the inverter so as to supply power to the load through the inverter when the AC power supply is determined to be abnormal and is deactivated;
a current detector that detects current flowing between the AC power supply and the converter; and
one or more processors that perform the following:
extracting a DC component from the detected current flowing between the AC power supply and the converter; and
when the extracted DC component is greater than a prescribed threshold current, causing the converter to stop operating and causing DC voltage from the DC power supply to be supplied to the inverter.
2. The uninterruptible power supply according to claim 1 , wherein said one or more processors further cause the converter to restart once a first prescribed period of time has elapsed from when the converter was stopped due to the DC component being greater than the prescribed threshold current.
3. The uninterruptible power supply according to claim 2 ,
wherein said one or more processors generate a converter drive instruction signal that is forcedly changed to a low state whenever the DC component becomes greater than the prescribed threshold current, and returns to a high state after the first prescribed period of time has elapsed since changed to the low state, and
wherein said one or more processors cause the converter to stop and restart according to the high and low states of the converter drive instruction signal.
4. The uninterruptible power supply according to claim 3 , wherein said one or more processors cause operations of the converter, the inverter, and the DC power supply to stop, if the DC component becomes greater than the prescribed threshold current within a second prescribed period of time from when the converter is restarted.
5. The uninterruptible power supply according to claim 4 , wherein said one or more processors cause the operations of the converter, the inverter, and the DC power supply to stop on the basis of a logical product of a DC component leading edge signal indicating a state of the DC component and a delayed converter drive signal obtained by delaying a converter drive signal indicating a state of the converter by the second prescribed period of time.
6. The uninterruptible power supply according to claim 3 , wherein said one or more processors cause the operations of the converter, the inverter, and the DC power supply to stop if a number of times that the DC component becomes greater than the prescribed threshold current reaches a prescribed count that is at least two within a third prescribed period of time.
7. The uninterruptible power supply according to claim 6 , wherein said one or more processors increase a count each time that the DC component becomes greater than the prescribed threshold current and reset the count each time the third prescribed period of time elapses.
8. The uninterruptible power supply according to claim 2 , wherein said one or more processors cause operations of the converter, the inverter, and the DC power supply to stop, if the DC component becomes greater than the prescribed threshold current within a second prescribed period of time from when the converter is restarted.
9. The uninterruptible power supply according to claim 8 , wherein said one or more processors cause the operations of the converter, the inverter, and the DC power supply to stop on the basis of a logical product of a DC component leading edge signal indicating a state of the DC component and a delayed converter drive signal obtained by delaying a converter drive signal indicating a state of the converter by the second prescribed period of time.
10. The uninterruptible power supply according to claim 2 , wherein said one or more processors cause the operations of the converter, the inverter, and the DC power supply to stop if a number of times that the DC component becomes greater than the prescribed threshold current reaches a prescribed count that is at least two within a third prescribed period of time.
11. The uninterruptible power supply according to claim 10 , wherein said one or more processors increase a count each time that the DC component becomes greater than the prescribed threshold current and reset the count each time the third prescribed period of time elapses.
12. The uninterruptible power supply according to claim 1 , wherein said one or more processors include a DC component extractor having a low-pass filter that extracts low-frequency components.