A robust nonlinear backstepping control scheme for hybrid AC/DC microgrids to improve dynamic stability against external disturbances

Abstract

In this work, robust nonlinear controllers are designed for converters interfacing power generation and energy storage including DC- and AC-sides in hybrid AC/DC microgrid for improving the dynamic stability against external disturbances. The robust switching control inputs for all these interfacing converters and excitation as well as steam-valving control laws for the synchronous generators are determined using a nonlinear backstepping approach. The dynamic elements of the hybrid AC/DC microgrid are modeled by considering the effects of external disturbances where these disturbances reflect the effects of modeling errors, measurement noises, and parametric uncertainties. The robust control inputs for different elements in the microgrid are determined by guaranteeing the convergences of all relevant states, associated with different elements, toward their desired values while properly bounding the effects of disturbances. Control Lyapunov functions (CLFs) are formulated, during the proposed controller design process, to assess the dynamic stability. Simulation studies are conducted on a hybrid AC/DC microgrid to validate the effectiveness by observing the overall power balance with changes in the system while comparing with an existing sliding mode controller (ESMC). Simulation results clearly indicate robustness of the newly proposed controller through the improvement in the overall dynamic performance of the hybrid AC/DC microgrid over the ESMC.