A comparison of virtual circuit-based control designs for half-bridge converters with LCL output filters

This paper compares the design and performance of two controls for half-bridge converters with LCL output filters based on Virtual Circuit Design method, which is an intuitive way to achieve desired closed-loop behaviours as well as resonance damping and low-frequency behaviours. The first control is represented by a circuit employing a resistor in series with a converter-side inductor to stabilize the resonance while the second one by a resistor in parallel with a filter capacitor. This yields different low-frequency behaviours and different designs of the current controllers. Moreover, both circuits feature the adjustable virtual inductance to improve the bandwidth and the robustness. The experiment illustrates excellent performances from the step response and fair robustness against grid-inductance variation.