Power quality improvement at medium-voltage grids using Hexagram Active Power Filter

A new Hexagram Active Power Filter (APF) is proposed for harmonics elimination at medium-voltage grids. The new converter is composed of six interconnected three-phase standard two-level voltage source converter modules with advantages including modular structure with easy construction and maintenance, no voltage unbalance problem, reduced voltage stress, symmetrical structure with automatic and equal voltage and current sharing, and easy control with well-developed two-level control techniques, etc. In this paper, One-Cycle Control - an excellent control scheme for two-level converters is extended to realize the control of the Hexagram converter for active power filter function. Both simulation and experiment have been conducted and verified the proposed converter and proposed control scheme.