Robust H∞ controller design for microgrid-tied inverter applications

This paper proposes an H_∞ mixed sensitivity design of output current tracking controller in a stationary reference frame for general microgrid-tied inverter applications. Variations in a microgrid impedance values have been modeled as multiplicative uncertainty in the plant model. Equivalent microgrid voltage has been considered as the output disturbance acting on the plant. Particular weighting functions have been introduced as part of the H_∞ algorithm. Weighting functions have been used for performance tuning by shaping the sensitivity and complementary sensitivity functions of the closed loop system. An 8th order H_∞ controller has been synthesized and system robust stability has been evaluated using modified impedance stability criterion. Controller regulating performance has been validated using PSIM software simulation. Despite the fact that no resonance damping technique is applied, system has shown to be robustly stable under predefined microgrid parameters variations.