UDE-based current control of grid-connected photovoltaic inverters

Abstract

Purpose The purpose of this study is to improve the control performance of grid-connected photovoltaic (PV) inverters with inductive-capacitive-inductive (LCL) filters by proposing a new robust current control based on uncertainty and disturbance estimator (UDE). Design/methodology/approach The control strategy combines the capacitor current feedback with a UDE-based control to solve robust stability issues in the presence of parametric uncertainties and disturbances. Findings This paper provides guidelines for tuning the controller parameters where it is shown to be easy to implement by simply selecting the appropriate feedback coefficient, the reference model and an approximate lumped disturbance bandwidth. Simulation and experimental results demonstrate the effectiveness of the proposed controller in terms of resonance damping, tracking performance and robust stability under grid uncertainties and disturbances. Practical implications This paper offers a new approach for designing implementable robust controllers for LCL-filtered grid-connected PV inverters. Originality/value A new UDE-based current control is proposed to improve the stability performance of grid-connected PV inverters. The advantages of UDE-based control are its simple structure, easy tuning and robustness under parameter uncertainties and disturbances. Simulation and experimental results support the theoretical findings.