Transformer-less 3P3W SAPF (three-phase three-wire shunt active power filter) with line-interactive UPS (uninterruptible power supply) and battery energy storage stage

Abstract

In this article, a transformer-less 3P3W SAPF (three-phase three-wire shunt active power filter) integrated into the distributed energy network which embeds line-interactive UPS and bi-directional chopper-fed energy storage equipment. The proposed system operates in two operating modes of line-interactive UPS (uninterruptible power supply) with bi-chopper-fed battery energy storage stage. In normal mode of operation, the main power supply current charges the standby bi-chopper fed battery energy storage equipment, in addition to APF feature. When the main power supply is severed, it operates as a backup power source to the load. The feasibility of the distributed energy network is improved, by eliminating the transformer and reduced power component, to provide accurate performance, less cost and reduced size as compare to previous topologies. The PI (proportional integral) controller ensures the regulated sinusoidal voltage with unity power factor, phase amplitude, and low THD (total harmonic distortion) into the distributed energy grid. For proper batteries energy storage stage, active power filtering and UPS operation, the SRF (synchronous-reference-frame) method with PLL (phase locked loop) scheme is implemented. The test result of 5 kW prototype system tested in simulation and laboratory validates the claimed performance in the distribution power energy network.