Novel Power Smoothing Technique for a Hybrid AC-DC Microgrid Operating with Multiple Alternative Energy Sources

The power produced by renewable sources such as photovoltaic systems and wind energy conversion systems is highly intermittent due to continuously changing irradiance and wind velocity. When the distributed generation systems employing photovoltaic (PV) array and wind energy conversion system (WECS) operate in grid-tied mode, the power fluctuations affect the power quality of the grid. In a hybrid AC-DC microgrid (HMG), the dynamics of DC and AC subgrids influence each other. This paper proposes a supercapacitor based novel power smoothing methodology for the HMG with PV array, WECS, fuel cell (FC) and electrolyzer (EL) based hydrogen storage system considering the power fluctuations in both subgrids. The power smoothing technique on the DC subgrid aims to facilitate instantaneous power balance. The Kalman filter (KF) based velocity smoothing (KFV) approach is developed for the WECS. The KFV technique is compared with the power smoothing techniques presented in the literature. The KFV method is found to be effective in computing the smooth power reference for the supercapacitor system. By incorporating the proposed power smoothing technique in the HMG, the stress on the interlinking converter (ILC) and utility grid are minimized and the power quality is enhanced.