Systematic multi-variable H∞ control design for primary frequency regulation in stand-alone microgrids with high penetration of renewable energy sources

In this paper, a systematic design of a robust multi-variable control structure for primary frequency regulation in microgrids with high rate of renewable source penetration is proposed. The considered microgrid represents a diesel-photovoltaic-supercapacitor hybrid power generation system operating in stand-alone mode. The proposed control structure relies on a two-level architecture: classical PI-based current tracking controllers are placed on the low control level and receive references from an H∞ control-based upper level. A comprehensive methodology that casts the specific engineering demands of microgrid operation into H∞ control formalism is detailed. It is also shown how closed-loop dynamical performance requirements must at their turn be taken into account in the initial microgrid setup and sizing, namely in choosing and rating the energy storage system. Numerical simulations carried out in MATLAB®/Simulink® show the effectiveness of the proposed H∞ robust control strategy on a MVA-rated microgrid.