Harmonic Power Sharing With Voltage Distortion Compensation of Droop Controlled Islanded Microgrids

Harmonics are found to have deleterious effects on power system equipment including transformers, capacitor banks, rotating machines, etc. However, the distributed generation interfacing converters (DICs) are able to improve power quality and system efficiency in case of adding a flexible control strategy. This paper describes the voltage distortion generated by nonlinear loads and proposes a new harmonic droop control to reduce the voltage harmonic distortion at the point of common coupling (PCC) and to share the harmonic power between parallel islanded inverters controlled by classical frequency droop method. The main objective it to effectively compensate the harmonic currents drawn by each DIC to supply the nonlinear loads in parallel with voltage harmonic damping at PCC. The operation principle of the proposed harmonic droop is explained in details. Modeling and stability analysis are developed in order to define the control parameters suitable for proper operation. Simulation and experimental results are presented to show the competence of the proposed algorithm in achieving harmonic power sharing and in improving the voltage harmonic distortion at the PCC.