Abstract: The invention proposes a power sharing control strategy based on the Linear Quadratic Regulator with optimal reference tracking (LQR-ORT) for three-phase inverter-based generators using LCL filters in both grid-connected and islanded modes. The use of an LQR-ORT controller increases robustness margins and reduces the quadratic value of the power error and control inputs during transient response. Supplementary loops are also used to avoid frequency and voltage deviations in the AC bus without communications. These supplementary loops are used to achieve proportional power sharing among generators according to their rated power capacity. A synchronous reference frame model, which integrates dynamics of power sharing and voltage-current (V-I) control loops, is also proposed. Experimental results demonstrate accuracy of the proposed invention and the effectiveness of the LQR-ORT controller on improving transient response, power sharing, and voltage and frequency recovery.