An Adaptive AC Input Monitoring Algorithm for Microprocessor Controlled Parallel Processing UPSs

This paper describes a basic, adaptive ac-input algorithm applied to a microprocessor-controlled parallel-processing Uninterruptible Power Supply (UPS) with a short battery holdover. The algorithm dynamically modifies the ac-input line switch operating-thresholds, which are based an the UPS output load current and ac-input voltage, ensuring that battery-energy is preserved for periods in whtch the UPS load requires inverter-battery source power.