Optimal Control Parameter Design for Dual-Loop Controlled Grid-Forming VSCs

Renewable energy/energy storage is generally integrated into microgrids with grid-forming voltage source converters (VSCs). The control parameter design of grid-forming VSCs is one of the most challenging techniques because of the inherent resonant phenomenon and the coupling issues between the current and voltage variables. This paper provides a simple approach to achieve the optimal parameter design of dual-loop control for grid-forming VSCs. The optimal parameter design is conducted for the current inner-loop and voltage outer-loop independently without any coupling. Moreover, in the proposed design, standard analysis and design tools, e.g., Pole-map and Bode-plot can be directly employed and complex formula solving is needless. Therefore, the proposed approach is easy to implement in practical. In addition, it has been identified that the proportional controller in the outer-loop has a negligible impact on the control bandwidth and thus can be removed to further simplify the design process and control structure. The left resonant controller can then be refined to achieve a significantly improved dynamic performance of the output voltage of VSCs. The effectiveness and performance of the design approach are carefully verified by experimental results.