Performance specifications of series-parallel UPS's with different control strategies

Abstract

In this paper, two control strategies for three-phase Series-Parallel Uninterruptible Power Supplies (SP-UPS) are described and compared. An SP-UPS consists of a parallel and a series converter, and most of the power required by load is supplied directly from ac input line during standby mode. Therefore, the overall efficiency is increased as compared to conventional UPS's. The first control strategy proposed for SP-UPS was based on voltage control of series converter and current control of parallel converter. However, recently an opposite strategy has been proposed, i.e., voltage control of parallel converter and current control of series converter. This paper compares these two control strategies. The comparison is made based on different performance criteria like seamless transition between backup and standby modes, dynamic performance, reference generation and the size of filters. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved.