A high-power multi transistor-inverter uninterruptable power supply system

Abstract

The active and reactive load distribution between n paralleled single-phase UPS inverters is equalized by virtue of n − 1 load sharing control loops. The approach permits the construction of UPS systems of any desired power rating at maximum utilization of the power components. The method of harmonic cancellation decreases the switching frequency of the power devices while maintaining good dynamic performance. The design details of a 45 kVA UPS inverter system with 150 % steady-state overload capability are presented. The performance at various operating conditions is illustrated by oscillograms.