Power factor correction of uninterrupted power supply systems

An Uninterruptible power supply (UPS) is used to avoid the main power line interrupting by supplying a load. Nowadays most critical loads (Devices) are connected to an on-line UPS system to avoid all problems coming from the main power supply. Usually, the uninterruptible power supply system is considered as backup power for the electrical system, because critical load applications always rely on the UPS system to uphold continuous power, when the main power source conditions are abnormal. Today reduction of line current harmonics or power factor correction is very necessary and in order to improve that, there are two types of power factor correction, passive PFC, and active PFC. Most commercial UPS systems used the passive power factor correction by using line LC filters to reduce the cost of the system. The objective of this thesis is to improve the minimum Total Harmonic Distortions (THD) and PF nearly unity, by using Full-Bridge rectifier with Boost converter as an APFC with Average Current mode Controller (ACMC) using two PI Controller. In this thesis, we design and compare APFC of a different kind of UPS system (simple UPS without PFC, Off-line UPS with active PFC, and On-line UPS with active PFC) in the input and output sides for an approximately 800 VA UPS system. A full-bridge double conversion topology was selected for its simplicity and the design topology was implemented by using the Matlab-Simulink software program to demonstrate a proof of concept for the UPS system. As a result, we get a power factor nearly unity in the Input and output side and the total harmonic distortions are reduced to around 4%. Key words: Off-Line, On-Line, PFC, PI Control, THD, UPS.