Abstract—This paper deals with various active damping
approaches for PI-based current control of grid-connected
pulsewidth-modulation (PWM) converters with LCL filters, which
are based on one additional feedback. Filter capacitor current,
as well as voltage feedback for the purpose of resonance damping,
are analyzed and compared. Basic studies in the continuous
Laplace domain show that either proportional current feedback
or derivative voltage feedback yields resonance damping. Detailed
investigations of these two approaches in the discrete z-domain,
taking into account the discrete nature of control implementation,
sampling, and PWM, are carried out. Several ratios of LCL
resonance frequency and control frequency are considered. At
high resonance frequencies, only current feedback stabilizes the
system. At medium resonance frequencies, both approaches have
good performance. At low resonance frequencies, stability gets
worse, even though voltage feedback offers slightly better damping
properties. Measurements validate the theoretical results.