Development of a novel power apparatus to make up for voltage dips and interruptions based on quick reversible operation of a PWM converter

Along with wide and deep penetration of electronics application into our modern society, voltage dips and momentary interruptions, mainly due to lightning and snow damage on overhead transmission lines, have become a disturbance to normal operation of loads. A UPS, which is mostly employed to protect sensitive loads from disturbances, has such limitations that it dissipates no less energy in running operation because currents flow through two converters in series, it is poor in feeding electric motors which occupy the main loads in industrial plants and that its costs are high to be commonly applied. UPS can be regarded not as omnipotent against voltage dips and short interruptions. We have developed a novel power apparatus termed QBS (quick backup system) to supplement the above drawbacks in UPS, employing one reversible AC/DC converter and one high-speed switch. Normally QBS supplies power directly from a commercial network to critical loads while the reversible converter interconnects with it to charge the battery. When the critical bus voltage deviates from the tolerance range QBS disconnects the high-speed switch and continues to feed the critical loads in UPS mode. The whole power transition is completed within 2 ms. QBS of several thousands kVA has already been put to commercial use in telecommunication centers, electronics manufacturers and others.