Optimal Controllers Design for Microgrid Inverter Based on Disturbance Rejection Approach

During islanded operation in microgrids, a clean and balanced sinusoidal output voltage is required at the point of common coupling (PCC). To reduce the harmonic content at the PCC, an optimal control strategy based on disturbance rejection is proposed in this paper. First, an augmented error dynamic system included the future information of the reference voltage, the history information of repetitive control, and the current information of the system state vector is built Second, a particular mathematical transformation method is employed to eliminate the augmented error dynamic system’s time delay, which makes it suitable for general optimal theory. Based on this, in combination with the fundamental equivalent input disturbance (EID) theory, the influence of disturbance at the PCC is eliminated, and the recovery time of repetitive control systems is shortened. Finally, the simulation and experiment results verify the effectiveness of the proposed control strategy.