Robust Passivity-based Control Integrated with UDE Strategy for Grid-Tied Inverter

Abstract

Uncertainties caused by parametric variations, external disturbances, and modelling errors of grid-tied inverters (GTI) make it challenging to select a proper gain for the desired controller. The performance of conventional passivity-based controller (PBC), which depends on a strictly accurate mathematical model of the system, is seriously deteriorated due to having poor robustness against parametric uncertainties and disturbances. To this end, this paper presents an improved passivity-based controller scheme assisted with uncertainty and disturbance estimator (UDE) for GTI. The UDE that has been adopted into the proposed UDE-PBC loops is used to simultaneously estimate uncertainties, which can achieve robust control and provide zero steady-state error. Moreover, the proposed UDE-PBC enables a two-degree-of-freedom (2DOF) control structure; one dedicated for disturbance rejection and the other for closed-loop tracking response of GTI system. The effectiveness of the proposed control scheme has been verified in an experimental prototype of 2 kW and compared with the base controllers in terms of robustness and transient response.