Microgrids, which have been developed to cope with the penetration of renewable energy systems, can provide a promising solution to integrate renewable and distributed energy resources and distributed energy storage systems. Microgrids now play an important role in the improvement of the stability, reliability and power quality of power systems. In microgrids with nonlinear loads, current harmonics may induce voltage distortion of the point of common coupling (PCC).
Load power sharing and voltage quality are more challenging in islanded microgrids with nonlinear loads. Distributed generations (DGs) can be used to improve the power quality in microgrids. However, the conventional droop control can cause poor harmonic power sharing among the DGs due to mismatched line impedance.
Kim Sung Hyok, a researcher at the Faculty of Electrical Engineering, has proposed a harmonic power-sharing control method using the adaptive regulation of virtual harmonic impedance. He used consensus algorithm to regulate the virtual harmonic impedance with mismatched line impedance in consideration. The consensus-based distributed control does not require prior knowledge of line impedance.
The simulation results show that the proposed method is appropriate for achieving accurate harmonic power sharing while reducing the voltage distortion at the point of common coupling (PCC).
For more information, you can refer to his paper “Voltage Harmonic Compensation Using Virtual Harmonic Impedance Regulation in Islanded Microgrids” in “Journal of Electrical Power & Energy Systems” (EI).