Efficient Virtual Impedance-Based Active Damping for LCL Filter Resonance in Grid Connected Inverter Using Inverter and Grid Current as Feedback

LCL filter resonance complicates the design of a current control loop, threatens its stability, and increases harmonic content in output current at the resonance frequency. This paper presents a novel active damping approach based on the virtual resistor. The proposed method utilize the inverter side current and grid side current as feedback variable to provide the virtual effect of three different damping resistors. The derived feedback gains are free from frequency terms and so do not contain any differential and integral terms which makes their implementation easy, requires less computation, and avoids noise amplification in the current control loop. Importantly, this method does not require any extra voltage/current sensor, the sensor already in use for current controlling and protection purposes is utilized for the implementation of the proposed active damping. Finally, the proposed method is simulated using MATLAB/Simulink and the simulation result justify the effectiveness of the proposed method.