Enhanced power calculator for droop control in single-phase systems

Droop control is a common method to parallel operation of inverters. This method uses the average values of power components which are usually obtained through low-pass filters. However, in single-phase systems the power components are oscillating at twice fundamental frequency and the filters cut-off frequency must be very low. Thus, there is a tradeoff between dynamic response and oscillation attenuation. In this paper, a method that uses a fictitious quadrature reference frame to calculate the average power components is presented. This method improves the dynamic response of the power sharing control and eliminates the double-frequency oscillation over the voltage and frequency synthesized by the inverter. Moreover, it is able to deal with nonlinear loads since the harmonic components that appear in the instantaneous power are filtered. This paper also presents a comparison between this method and the classical one through simulation carried out in Matlab/Simulink and experimental results.