Uninterruptible Power Supply Apparatus

Abstract: An AC input filter (2) includes a first reactor (12RA) having a first terminal connected to a second terminal of a switch (1) and a second reactor (12RB) having a first terminal connected to the second terminal of the switch (1). A converter (3) includes a first multilevel circuit (3A) connected between a second terminal of the first reactor (12RA) and first to third DC lines (L1 to L3) and a second multilevel circuit (3B) connected between a second terminal of the second reactor (12RB) and the first to third DC lines (L1 to L3). A control device calculates a first voltage, which is the sum of the voltages across the terminals of first and second capacitors (C1, C2), and a second voltage, which is the difference between the voltages across the terminals of the first and second capacitors (C1, C2). When an AC power supply is healthy, the control device controls the first and second multilevel circuits (3A, 3B) so that the first voltage goes to a reference voltage and the second voltage is eliminated. In the event of a power failure in the AC power supply, the control device controls the first and second multilevel circuits (3A, 3B) so that the second voltage is eliminated.

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