Notch-Filter Active Damping of LCL Filter Resonance in a Grid-connected Inverter with Variable Grid Inductance

摘要

The problem of LCL filter resonance is prominent in grid-connected voltage source converters with LCL filters. Various methods of damping the resonance have been proposed. This paper presents a simple but robust active damping solution based on a notch filter which is able to effectively damp the filter resonance for a range of grid impedance values. This scheme does not require measurement of the filter capacitor current, and therefore, does not increase the number of current sensors in the system. The notch filter active damping scheme is implemented in a grid-voltage sensorless virtual-flux based direct power control scheme, therefore, the only sensors required are grid current sensors. The model is created and analyzed in Matlab/Simulink and simulation results show that the system is stable, with a grid current THD of less than 5 % which met the grid requirements set by standard organizations..