Small-signal stability improvement of an islanded microgrid with electronically-interfaced distributed energy resources in the presence of parametric uncertainties

This paper deals with the concept of small signal stability (SSS) issue in an electronically-interfaced microgrid with large penetration of distributed energy resources (DERs) subjected to the parametric uncertainties. Utilizing a method to enhance SSS of the system stemmed from industrial experiences is the first achievement of this study, which is realized by employing two extra feed-forward loops in the power controller section of DER unit. This control structure damps the active and reactive power oscillations by shifting the dominant eigenvalues to the left half-plane (LHP) in case of any changes in the operating point or droop coefficients. For investigating the impacts of parametric uncertainties on the overall stability, the basic theorem of the proposed robust control strategy, frequency-domain modeling of the microgrid, robustness and close-loop stability analyses are outlined. This method shows that improving the power control section topology results in higher stability margins in case of uncertain load perturbations. Furthermore, it demonstrates how much load variations are allowed to preserve SSS of the system in the frequency-domain which is a more convenient approach and takes less time than time-domain simulations. Finally, time-domain simulations conducted in MATLAB/Simulink on the sample test system will show proper results of the frequency-domain findings.