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This paper describes an improved universal active power line conditioner designed to attenuate every disturbance in the electric power system and critical loads, except frequency variations. The circuit has a series voltage filter and a parallel current filter interconnected through a shared dc bus. In case of a supply interruption, the current filter reconfigures to UPS and feeds a pre-selected 20% of load during 500 ms at the expenses of the dc bus. Over previous reconfigurable solutions, the input and output series static switches have been eliminated improving the reliability, efficiency and cost. Optional parallel LC tuned current filters have also been proved to be control compatible. The search has been guided by an iterative analysis+synthesis cost comparative method, initiated in previous works, showing the cost of the components involved in each explored topology. Experimental results on three laboratory models and a 400 kVA industrial prototype validate the topology and suggest improvement of some control loops. Index Terms--Active filter, hybrid current filters (new index term proposed), load flow control, power conditioning, power line filter, power quality, pulse with modulation, uninterruptible power systems.

The innovation brought by the introduction of new technologies in our modern society has also started to appear in education. The biggest efforts come from the institutions involved in distance education, partly due to the characteristics of the educational system they represent. In order to improve the technology development there are a large number of projects being developed inside the European Union. Index Terms--Distance education, European Union projects, technology resources and innovation.

This paper presents a critical analysis of various topologies for power circuits used in power line conditioners designed to attenuate or remove disturbances in the electric power system. By defining a series of merit figures, it becomes possible to appraise the desirable qualities shown by the technical and economical aspects in each configuration. There is also a description of the basic lines for designing practical equipment. Finally, experimental results of a novel topology which reconfigurates to UPS operation in the case of a power line failure are shown to confirm the validity of the prospective method. Index Terms--Active power filter, active power line conditioner, harmonic distortion, power quality.