Dedicated power-line UPS for power plants, substation design, with online, zero-delay transfer function, mainly in the load on the voltage requirements of the higher places, such as power remote, RTU, power line carrier, monitoring. Mains normal, single-phase 220V AC (or three-phase 380V) After isolation, rectifier to the inverter power supply after filtering; if AC input power failure, will be owned by the DC power system through the anti-anti-diode screen to the inverter supply power, and then through to the important post-output isolation load; if the DC panel power, then still AC input power; if the inverter overload or failure, by the static bypass switch to power.