Adaptive damping scheme of LCL filter resonance under inductance variation for a single-phase grid-connected inverter

LCL-filter is broadly utilized to attenuate the switching harmonic ripple generated from the PWM (Pulse Width Modulation) based converters and inverters. However, due to the resonance problem the stability issue should be overcome. Among many solutions, notch filter based active damping is effective solution for not needing additional sensor and damping resistor. But that strategy is vulnerable to filter parameter variation, which varies the resonant frequency. This paper proposes adaptive notch filter concept for a single-phase inverter in considering parameter variation of two inductors with respect to current. Due to that estimation performance, it provides with a size and cost-effective solution for selecting filter materials. Also, this adaptive filter can be designed narrower, which realizes less phase attenuation, thereby securing more loop gain of total system. Therefore, current control loop secures higher bandwidth. Simulation verification of the proposed method is given through MATLAB/Simulink and PSIM software.