A Robust Design of Active Damping With a Current Estimator for Single-Phase Grid-Tied Inverters

This paper presents an improved control scheme for the operation of grid-tied inverters in order to attain the IEEE 1547.2-2008 harmonic limit standard even with a wide range of grid parameters. This control structure includes an active damping with a new current estimator and a proportional-resonant controller with harmonic compensation. In order to guarantees the inverter operation with a wide range of grid parameters, the damping and the controller gains are designed considering robustness characteristics. Moreover, it proposes a new estimator for the current filter capacitor for operation with a wide range filter resonance frequency. The grid synchronization mechanism uses the modified second-order general integrator frequency-locked loop technique. Experimental results are carried out and presented to validate the control structure design and the proposed current estimation.