An RL-Type Active Damper for Stabilizing Wide Band Oscillations in Grid-Tied Inverter Systems

The grid-tied voltage-source inverter system may suffer from the stability issues due to the impedance mismatch between the converter and the grid. Paralleling an active damper at the PCC point provides a convenient solution. Like the parallel stabilizers in DC system, the active damper in grid-tied inverter system can be regulated as a virtual resistor, inductor or capacitor. The comparison among them has been analyzed using the passivity-based stability criterion in this paper, and the shaped inverter output admittance in complex plane diagram can directly explain their different characteristics. Based on these analyses, an RL-type active damper regulation method combining a resistive active damper and an inductive one is proposed to extent its effective stabilization frequency range in a wide band, which is verified by the simulation. The experimental results also validate the proposed method.