Uncertainty and disturbance estimator based current control of LCL-Filtered grid-connected inverters

This paper proposes a new current control strategy for LCL-filtered grid-connected inverters based on the uncertainty and disturbance estimator (UDE). To ensure system stability, the LCL filter resonance is actively damped using the classical approach of feeding back the filter capacitor current giving rise to a combined active damping with UDE based control structure. The UDE based control method uses the known part of system model while the terms including unknown dynamics are treated as additional system uncertainties and disturbances, then appropriately estimated and canceled. The effectiveness and robustness of the proposed method are demonstrated through simulation results.