Frequency and voltage control of microgrids upon unintentional cascading islanding

Microgrids are small scale electricity networks comprising diverse distributed resources (DER) which can operate in grid-connected or islanded mode. An islanding situation may occur in a cascading way, where the DER types inside the islanded area have substantial impacts by means of control schemes. This paper presents a comprehensive study of the islanding process and the subsequent frequency and voltage control of different island schemes that comply with the IEEE 1547.4 grid code. Grid-connected operation, transition-to-island and islanded-mode operation of three different forms of cascading islanding were investigated. Studied islanding forms were a synchronous generator, inverter-based DER and a hybrid type. Experimental results are given in addition to simulation studies.