| 摘要 |
An uninterruptible power supply (UPS) system is provided which is adapted to prevent the output voltage from dropping due to an operation delay of a relay for isolating an AC power source side from the UPS system, and along with this, to avoid an unexpected current flowing between the AC power source side and the UPS system side. When a short circuit occurs, a parallel converter (2), connected in parallel to input terminals (11) connected to an AC power source (1), is made to operate so that the output voltage thereof becomes "0", and a series inverter (3), connected in series between an input relay (7) and one of output terminals (12), is made to carry out a compensating operation with a smoothing capacitor (4) taken as a power source so that the value of the applied voltage to the output terminals (12) becomes an output voltage command value Vout*. This makes the output voltage of the parallel converter (2) become "0" to produce no electric potential difference between the AC power source (1) side and the output side of the parallel converter (2). Therefore, no current flows between the AC power source (1) side and the parallel converter (2), and the value of the applied voltage to the output terminals (12) is continuously maintained at the output voltage command value Vout* by the series inverter (3). <IMAGE> |
