| 摘要 |
Conventional uninterruptible power supplies require different power conversion stages and other systems, during normal "break even" operation, have minimum inverter currents under zero load conditions. An uninterruptable power supply and line conditioner uses a local battery (40) and the utility power lines (96, 98) as the sources of power for an AC load, and in which a pulse width modulation (PWM) inverter (46) is used to convert the battery DC to the load AC and to charge the battery from the power lines. The utility power lines (96, 98) are effectively connected to the load by way of a series inductance (78), and the phase angle between the inverter (46) output voltage and the effective input voltage to the inductance (78) from the power lines controls the proportioning of current to the load and to the battery (40) from the power lines, and from the inverter to the load. The necessary inverter current is reduced and the throughput efficiency improved by, in effect, providing a predetermined ratio R between the voltage applied to the input side of the inductor and the voltage at the inverter output; in a preferred embodiment the effective input voltage is about 1.1 times the inverter voltage, and is produced by use of magnetic shunts (114, 116) in a transformer (78) which couples the utility line to the load. |
