Systematic control design for half-bridge converters with LCL output filters through virtual circuit similarity transformations

This paper presents the systematic design and performance of two controls for half-bridge converters with LCL output filters based on a similarity transformation. This type of converters is commonly used in, for example, grid or battery interfaces. Both controls feature active damping, i.e. filter resonances are damped through software and not by using passive resistors. Moreover, both controls are designed using the Virtual Circuit Design method, which is an intuitive way for designing controls with closed-loop behaviour specified by means of a - virtual - reference circuit through a similarity transformation. The converters controlled through virtual circuit inherit many properties of their underlying reference circuit, including resonance damping, robustness and low-frequency behaviour. The experimental results demonstrate both controls to properly damp resonances. At low frequencies the first design presents itself as a resistor while the second design acts as an inductor. Supervisory current controllers treat the system accordingly.