Three-Phase Series Active Power Filter Without Isolation Transformer and Active DC Source

In this paper we propose two three-phase series active power filters (SAPF) for voltage harmonic compensation and voltage regulation. The power filters are conceived to operate without isolation transformer and auxiliary active dc source. The topologies are adequate for applications in which the load or grid terminals are accessible. The model of the systems are derived to analyze their behavior for general grid voltages and load conditions. Such analysis shows that it is possible to operate with a load active voltage amplitude regulated at the rated reference value for some grid voltages and load conditions. Based on the system analysis, a control strategy is proposed to adequately control the system. Experimental results for the system operating with very distorted input grid voltages are presented.