Transformerless Single-Phase Universal Active Filter With UPS Features and Reduced Number of Electronic Power Switches

This paper presents an universal active power filter for harmonic and reactive power compensation with uninterrupted power supplies (UPS) features. The configurations does not use transformer in the series part. Transformerless modern UPS systems have been rapidly replacing the old technology due to their performance and size attributes. Reducing the numbers of passive elements and/or switches in active power filters and UPS topologies not only reduces the cost of the whole system but also provides some advantages, such as great compactness, smaller weight, and higher reliability. However, the cost reduction requires the use of more complex control strategies. The model of the proposed system is derived and it is observed that the system can be reconfigurable to operate with four or three leg depending on the issue. A complete control system, including the pulsewidth modulation techniques, is developed and a comparison between the proposed filter and the standard one is done, as well. Simulated and experimental results validate the theoretical considerations.