“…The reactive power capability chart of the DG units, illustrated in Fig. 1, closely mapping that of modern variable speed wind turbines is modeled with two symmetric sigmoid functions (23) and (24) for the lower and upper limits respectively. For active power generation, P G i,t , above 15% of the maximum capability, an inductive and capacitive limit for reactive power of 0.5 times the maximum active power generation is enforced.…”