Analysis and design of cutoff frequency for power calculation low-pass filters in droop control

Droop control method has been widely applied to achieve equal power sharing among distributed generations in microgrids. In practice, low-pass filters are usually required to mitigate the harmonics and noises in the calculated instantaneous power and obtain the average power used for the generation of frequency and voltage references. Unfortunately, the design of low-pass filters has not been studied systematically in the existing research. This paper, by proposing a small-signal model of the droop controlled system, analyzes the effects of the low-pass filters on system stability and provides a design method for an optimal cutoff frequency. The effectiveness of the proposed design method is verified by simulations.