Simple Active Damping Solution for Industrial Grid-Tied Inverters Using LCL Filters

Grid-tied power inverters are typically interfaced with damped LC or LCL filters to limit the injection of switching harmonics. To minimize filter losses, the damping resistance of the filter is often reduced, resulting in poorly damped or unstable conditions at the resonant frequency. Therefore, different active damping solutions have been proposed in the literature to reduce passive elements while avoiding unstable conditions. However, most available solutions require additional current sensors or implement complex active damping algorithms. Moreover, the literature provides only partial guidelines to tune the active damping parameters. Therefore, this paper proposes a sensorless active damping solution based on a resonant current estimator and provides a straightforward tuning for its parameters. The proposed active damping method is experimentally tested on a three-phase, two-level 30 kVA inverter, thus demonstrating the validity of the presented approach.