2018 Volume 7 Issue 6 Pages 454-461
A grid-connected inverter is equipped with an LCL filter at its output. This filter has a resonant characteristic and many active damping methods have been researched to suppress the resonant effects. The inverter is often controlled digitally and there is a control time delay, which is inevitable due to A/D conversion, computation times, etc. This delay degrades the stabilities and damping effects of the inverter because the frequency characteristics are different from the designed one, especially around the resonant frequency. This paper proposes a simple and effective compensation method of the control time delay to improve the damping effects. It is based on an estimation method of future state values advanced by the delay time. The proposed method is applied to the grid-connected inverter control and its effectiveness is investigated and validated through determining transfer functions of the regulated current errors by experiment.
